Torque detection apparatus and electric power steering apparatus

ABSTRACT

The torque detection apparatus detects torque using torsion of a torsion bar. The torque detection apparatus includes a first rotating shaft and a second rotating shaft connected with a torsion bar in which torsion is produced when torque is applied, at least one optical scale that moves with rotations of the first rotating shaft and the second rotating shaft, at least one optical sensor that is paired with the optical scale, and detects the polarization of transmissive light or reflected light, the polarization varying depending on a position where light source light is passed through or reflected on the optical scale, and a computing unit that computes a relative rotational angle of the optical scale with respect to the optical sensor, and computes rotational displacements of the first rotating shaft and the second rotating shaft.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a National Stage of International Application No.PCT/JP2012/078208, filed on Oct. 31, 2012, which claims priority fromJapanese Patent Application Nos. 2011-239795, 2011-239797, 2011-239800,filed on Oct. 31, 2011, and 2012-190487, filed on Aug. 30, 2012, thecontents of all of which are incorporated herein by reference in theirentirety.

FIELD

The present invention relates to a torque detection apparatus and anelectric power steering apparatus.

BACKGROUND

Patent Literature 1 discloses a technology for a magnetic torque sensorthat can detect any one or both of a rotational angle and a rotationspeed in addition to torque, that can be reduced in size, and that canreduce production costs.

CITATION LIST Patent Literature

Patent Literature 1: Japanese Laid-open Patent Publication No.2010-190632

SUMMARY Technical Problem

To improve the resolution of a torque sensor, an optical torque sensorcan be used instead of a magnetic torque sensor disclosed in PatentLiterature 1. However, optical torque sensors are affected more byforeign substances and the like, and by fluctuations in the amount ofdetected light. Torque sensors are susceptible to foreign substances inparticular, because torque sensors require a plurality of optical scalesand optical sensors that are paired with the respective optical scales.

The present invention is made in consideration of the above, and anobject of the present invention is to provide a torque detectionapparatus and an electric power steering apparatus that are lessaffected by fluctuations in the amount of detected light and have animproved resolution.

Solution to Problem

According to an aspect of the present invention in order to solve theabove problems, there is a torque detection apparatus that detectstorque using torsion of a torsion bar, the torque detection apparatusincluding: a first rotating shaft and a second rotating shaft that areconnected with a torsion bar in which torsion is produced when torque isapplied; a plurality of optical scales that move with rotations of thefirst rotating shaft and the second rotating shaft, respectively; anoptical sensor that is paired with the optical scale, and detectspolarization of transmissive light or reflected light, the polarizationvarying depending on a position where light source light is passedthrough or reflected on the optical scale; and a computing unit thatcomputes a relative rotational angle of the optical scale with respectto the optical sensor, and computes rotational displacements of thefirst rotating shaft and the second rotating shaft.

With this structure, the optical sensors detect the rotational angles ofthe respective optical scales moving with the rotations of the firstrotating shaft and the second rotating shaft, respectively, using thepolarization of the transmissive light or the reflected light thussplit. Therefore, the torque detection apparatus is less affected byfluctuations in the amount of detected light caused by foreignsubstances or the like although optical torque sensors are used,compared with when the light intensity of the transmissive light or thereflected light is directly detected. Because the tolerance of foreignsubstances is thus increased, the torque detection apparatus can be usedin an increased number of environments. Furthermore, even when opticaltorque sensors are used, the torque detection apparatus is less affectedby the fluctuations in the amount of detected light due to precisions inthe optical path (the distance from the optical scale to the opticalsensor). Therefore, the arrangement of the light sources and the opticalsensors can be designed more freely. In this manner, the torque sensorsin the torque detection apparatus can be reduced in size. Furthermore,the torque detection apparatus can also achieve a higher resolution,compared with a magnetic torque sensor.

According to a preferred aspect, it is preferable that a plurality ofwires are arranged on the optical scale in a manner not intersectingwith each other, and in such a manner that each of tangential directionsof the wires changes continuously.

With this structure, the polarization of the transmissive light or thereflected light is allowed to change correspondingly to the tangentialdirections of the wires, the polarization varying depending on theposition where the light source light output to the optical scale ispassed through or reflected. Therefore, the optical scale does not needto be provided with highly granular segments each having a differentpolarizing direction. As a result, the optical scale allows a highresolution to be achieved even when the size of the optical scale isreduced. When the size of the optical scale is reduced, the arrangementof the light source and the optical sensor can be designed more freely.Furthermore, the optical scale can have a higher heat resistance than aphoto-induced polarizer. Because the optical scale has a line patternwithout any intersections even locally, a highly accurate optical scalewith smaller error can be achieved. Furthermore, because the opticalscale can be stably manufactured through a bulk-exposure ornanoimprinting, highly accurate optical scales with smaller error can beachieved.

According to a preferred aspect, it is preferable that the tangentialdirections of the wires on the optical scale are oriented same amongareas in which intervals between adjacent wires are same, and thetangential directions of the wires are oriented differently among areasin which the intervals are different.

With this structure, a plurality of wires can be arranged easily in aconfiguration in which each of the tangential directions changescontinuously.

According to a preferred aspect, it is preferable that the opticalsensor uses a part of the wires whose tangential directions are orientedsame as a sensing area, and receives incident light that is the lightsource light passed through or reflected on the sensing area and beingincident on the optical sensor.

Such a structure enables the incident light to split into the firstpolarized light and the second polarized light. Therefore, the computingunit can calculate the polarization angle of the transmissive light orthe reflected light based on the signal intensities of the polarizedcomponents having the first polarization direction and the secondpolarization direction thus split. The first polarization direction andthe second polarization direction are preferably different from eachother by 90 degrees so that the computing unit can calculate thepolarization angle easily.

According to a preferred aspect, it is preferable that each of thetangential directions changes cyclically. With this structure, arelative displacement of the optical scale moved relatively to anoptical sensor can be easily recognized by measuring a change in thetangential direction.

According to a preferred aspect, it is preferable that the optical scaleincludes: a first grid pattern having a first cycle at which each of thetangential directions changes cyclically; and a second grid patternhaving a second cycle at which each of the tangential directions changescyclically and in which the number of cycles per one rotation isdifferent from that of the first cycle.

With such a structure, a relative displacement of the optical scale withrespect to the optical can be recognized by measuring a change in thetangential direction, whereby allowing an absolute angle of the opticalscale to be recognized easily.

According to a preferred aspect, it is preferable that the number offirst cycles per one rotation and the number of second cycles per onerotation are mutually prime.

With this structure, a relative displacement of the optical scale withrespect to the optical sensor can be recognized by measuring a change inthe tangential direction, whereby allowing an absolute angle of theoptical scale to be recognized easily.

According to a preferred aspect, it is preferable that a protectionlayer or a substrate covering the wires is provided. Such a structurecan reduce the possibility of foreign substances attached around thewires.

According to a preferred aspect, it is preferable that the wires areprovided as a plurality of layers in a thickness direction in which thetransmissive light or the reflected light is incident. Such a structurecan achieve a highly accurate optical scale with smaller error.

According to a preferred aspect, it is preferable that the opticalsensor includes: a first polarizing layer that splits incident lightthat is the transmissive light or the reflected light to a firstpolarization direction; a second polarizing layer that splits theincident light to a second polarization direction; a first photoreceiverthat receives first polarized light split by the first polarizing layer;and a second photoreceiver that receives second polarized light split bythe second polarizing layer.

With such a structure, the incident light is split into the firstpolarized light and the second polarized light. Therefore, the computingunit can calculate the polarization angle of the transmissive light orthe reflected light based on signal intensities of the polarizedcomponents having the first polarization direction and the secondpolarization direction thus split.

According to a preferred aspect, it is preferable that the firstphotoreceiver and the second photoreceiver on the optical sensor arepositioned alternatingly and spaced uniformly with each other.

With such a structure, the chances of the first photoreceivers and thesecond photoreceivers being blocked by a foreign substance byapproximately the same degree can be increased, so that the possibilityof the signal intensity output from one of the first photoreceiver andthe second photoreceiver dropping extremely can be reduced. Therefore,even when the intensity of the incident light is decreased by a foreignsubstance, the torque detection apparatus can detect a change in thepolarization direction of the transmissive light or the reflected lightin a manner less affected by foreign substances.

According to a preferred aspect, it is preferable that a polarizationaxis of the first polarized light is relatively different from apolarization axis of the second polarized light by 90 degrees. In thismanner, the computing unit can calculate the polarization angle easily.

According to a preferred aspect, it is preferable that the firstphotoreceiver and the second photoreceiver have a comb-like shapeengaging and spaced uniformly with each other. Therefore, even when theintensity of the incident light is decreased by a foreign substance, theoptical sensor can detect a change in the polarization direction of thetransmissive light or the reflected light, in a manner less affected byforeign substances.

According to a preferred aspect, it is preferable that the torquedetection apparatus further includes a light-shielding film that stopsthe incident light that is incident on the first photoreceiver and thesecond photoreceiver. Therefore, the optical sensor can adjust theamount of incident light, whereby allowing the reachable range of theincident light to be adjusted. As a result, the optical sensor candetect a change in the polarization direction of the transmissive lightor the reflected light highly accurately.

According to a preferred aspect, it is preferable that the computingunit calculates an absolute rotation angle of at least one of the firstrotating shaft and the second rotating shaft from a relative rotationangle of the optical scale with respect to the optical sensor, andoutputs a detected torque that is acquired from the rotationaldisplacements of the first rotating shaft and the second rotating shaft,and the absolute rotation angle. In this manner, the torque detectionapparatus can function as a torque angle sensor.

According to a preferred aspect of the present invention, it ispreferable that the electric power steering apparatus include the torquedetection apparatus, and the first rotating shaft and the secondrotating shaft be mounted on the steering shaft. With such a structure,the electric power steering apparatus can allow the torque detectionapparatus to detect a steering force of a driver communicated to aninput shaft via a steering wheel as steering torque.

Advantageous Effects of Invention

The present invention can provide a torque detection apparatus and anelectric power steering apparatus less affected by fluctuations in theamount of detected light and with an improved resolution.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic of a structure of an encoder unit according to afirst embodiment of the present invention.

FIG. 2-1 is a schematic for explaining an arrangement of an opticalscale and an optical sensor.

FIG. 2-2 is a schematic for explaining an exemplary modification of thearrangement of the optical scale and the optical sensor.

FIG. 3 is a block diagram of the encoder according to the firstembodiment.

FIG. 4 is a schematic for explaining an example of a wire grid patternon the optical scale according to the first embodiment.

FIG. 5 is a schematic for explaining an example of the wire patternaccording to the first embodiment.

FIG. 6 is a schematic for explaining a relation between a rotation angleand a polarization axis direction in the optical scale according to thefirst embodiment.

FIG. 7 is a schematic for explaining the relation between a rotationangle and a polarization axis direction in the optical scale accordingto the first embodiment.

FIG. 8-1 is a schematic for explaining the wire grid pattern on theoptical scale according to the first embodiment.

FIG. 8-2 is a schematic for explaining the wire grid pattern on theoptical scale according to the first embodiment.

FIG. 9-1 is a schematic for explaining the wire grid pattern on theoptical scale according to the first embodiment.

FIG. 9-2 is a schematic for explaining the wire grid pattern on theoptical scale according to the first embodiment.

FIG. 10-1 is a schematic for explaining the wire grid pattern on theoptical scale according to the first embodiment.

FIG. 10-2 is a schematic for explaining the wire grid pattern on theoptical scale according to the first embodiment.

FIG. 11-1 is a schematic for explaining a detection area of the opticalscale according to the first embodiment.

FIG. 11-2 is a schematic for explaining a detection area of the opticalscale according to the first embodiment.

FIG. 11-3 is a schematic for explaining a detection area of the opticalscale according to the first embodiment.

FIG. 11-4 is a schematic for explaining a detection area of the opticalscale according to the first embodiment.

FIG. 12-1 is a schematic for explaining an optical sensor according tothe first embodiment.

FIG. 12-2 is a schematic for explaining the optical sensor according tothe first embodiment.

FIG. 13-1 is a schematic for explaining splitting of incident light intopolarized components in the optical sensor according to the firstembodiment.

FIG. 13-2 is a schematic for explaining splitting of incident light intopolarized components in the optical sensor according to the firstembodiment.

FIG. 13-3 is a schematic for explaining splitting of incident light intopolarized components in the optical sensor according to the firstembodiment.

FIG. 14 is a schematic for explaining a relation between a rotationangle and a differential signal in the optical sensor according to thefirst embodiment.

FIG. 15-1 is a schematic for explaining an exemplary modification of theoptical sensor according to the first embodiment.

FIG. 15-2 is a schematic for explaining an exemplary modification of theoptical sensor according to the first embodiment.

FIG. 15-3 is a schematic for explaining an exemplary modification of theoptical sensor according to the first embodiment.

FIG. 16 is a schematic for explaining an exemplary modification of theoptical sensor according to the first embodiment.

FIG. 17 is a flowchart for explaining an optical sensor manufacturingprocess according to the first embodiment.

FIG. 18-1 is a schematic for explaining the optical sensor manufacturingprocess according to the first embodiment.

FIG. 18-2 is a schematic for explaining the optical sensor manufacturingprocess according to the first embodiment.

FIG. 18-3 is a schematic for explaining the optical sensor manufacturingprocess according to the first embodiment.

FIG. 18-4 is a schematic for explaining the optical sensor manufacturingprocess according to the first embodiment.

FIG. 18-5 is a schematic for explaining the optical sensor manufacturingprocess according to the first embodiment.

FIG. 18-6 is a schematic for explaining the optical sensor manufacturingprocess according to the first embodiment.

FIG. 19 is a schematic for explaining an exemplary modification of theoptical scale according to the first embodiment.

FIG. 20 is a schematic of a structure of an encoder according to amodification of the first embodiment.

FIG. 21 is a schematic of an encoder according to a second embodiment ofthe present invention.

FIG. 22 is a side view illustrating a structure of the encoder accordingto the second embodiment.

FIG. 23 is a schematic for explaining an example of a wire grid patternon an optical scale according to the second embodiment.

FIG. 24-1 is a schematic for explaining the wire grid pattern on theoptical scale according to the second embodiment.

FIG. 24-2 is a schematic for explaining the wire grid pattern on theoptical scale according to the second embodiment.

FIG. 25-1 is a schematic for explaining the wire grid pattern on theoptical scale according to the second embodiment.

FIG. 25-2 is a schematic for explaining the wire grid pattern on theoptical scale according to the second embodiment.

FIG. 26 is a schematic for explaining a relation between a rotationangle and a polarization axis direction in the optical scale accordingto the second embodiment.

FIG. 27 is a schematic of a structure of an encoder according to amodification of the second embodiment.

FIG. 28 is a schematic of an encoder according to a third embodiment ofthe present invention.

FIG. 29 is a schematic for explaining an example of a wire grid patternon an optical scale according to the third embodiment.

FIG. 30 is a schematic for explaining a relation between a rotationangle and a differential signal in the optical sensor according to thethird embodiment.

FIG. 31 is a schematic of a structure of an encoder according to amodification of the third embodiment.

FIG. 32 is an exploded perspective view for explaining main componentsof a torque sensor according to a fourth embodiment of the presentinvention.

FIG. 33-1 is a schematic for explaining an arrangement of optical scalesand optical sensors in the torque sensor according to the fourthembodiment.

FIG. 33-2 is a schematic for schematically explaining the optical scalesand the optical sensors in the torque sensor according to the fourthembodiment.

FIG. 34 is a schematic for explaining an arrangement of the opticalscales and the optical sensors in the torque sensor according to thefourth embodiment.

FIG. 35 is a block diagram of a torque detection apparatus according tothe fourth embodiment.

FIG. 36 is a schematic for explaining an exemplary modification of thetorque sensor according to the fourth embodiment.

FIG. 37 is a schematic for explaining an arrangement of optical scalesand optical sensors in a torque sensor according to a fifth embodimentof the present invention.

FIG. 38 is a schematic for explaining an arrangement of optical scalesand optical sensors in a torque sensor according to a sixth embodimentof the present invention.

FIG. 39 is a schematic for schematically explaining a torque sensoraccording to a seventh embodiment of the present invention.

FIG. 40 is a schematic for explaining an arrangement of the opticalscale and the optical sensor in a torque sensor according to the seventhembodiment.

FIG. 41 is a schematic for explaining an exemplary modification of thetorque sensor according to the seventh embodiment.

FIG. 42 is a schematic of a structure of a torque sensor according to aneighth embodiment of the present invention.

FIG. 43 is a side view of a structure of the torque sensor according tothe eighth embodiment.

FIG. 44 is a schematic of a structure of the torque sensor according toa modification of the eighth embodiment.

FIG. 45 is a schematic of a structure of an electric power steeringapparatus according to a ninth embodiment of the present invention.

FIG. 46 is a schematic of a structure of a robot arm according to atenth embodiment of the present invention.

FIG. 47 is a schematic of a structure of a robot arm according to amodification of the tenth embodiment.

FIG. 48 is a schematic for explaining an optical sensor according to aneleventh embodiment of the present invention.

FIG. 49 is a schematic for explaining an optical sensor according to atwelfth embodiment of the present invention.

FIG. 50 is a schematic for explaining an exemplary modification of theoptical sensor according to the twelfth embodiment.

FIG. 51 is a flowchart for explaining an optical sensor manufacturingprocess according to a thirteenth embodiment of the present invention.

FIG. 52-1 is a schematic for explaining the optical sensor manufacturingprocess according to the thirteenth embodiment.

FIG. 52-2 is a schematic for explaining the optical sensor manufacturingprocess according to the thirteenth embodiment.

FIG. 52-3 is a schematic for explaining the optical sensor manufacturingprocess according to the thirteenth embodiment.

FIG. 52-4 is a schematic for explaining the optical sensor manufacturingprocess according to the thirteenth embodiment.

FIG. 52-5 is a schematic for explaining the optical sensor manufacturingprocess according to the thirteenth embodiment.

FIG. 53-1 is a schematic for explaining manufacturing of a polarizinglayer in the optical sensor manufacturing process according to amodification of the thirteenth embodiment.

FIG. 53-2 is a schematic for explaining manufacturing of the polarizinglayer in the optical sensor manufacturing process according to themodification of the thirteenth embodiment.

FIG. 53-3 is a schematic for explaining manufacturing of the polarizinglayer in the optical sensor manufacturing process according to themodification of the thirteenth embodiment.

FIG. 54-1 is a schematic for explaining manufacturing of the polarizinglayer in the optical sensor manufacturing process according to amodification of the thirteenth embodiment.

FIG. 54-2 is a schematic for explaining manufacturing of the polarizinglayer in the optical sensor manufacturing process according to themodification of the thirteenth embodiment.

FIG. 55 is a schematic for explaining an example of the optical sensoraccording to the thirteenth embodiment.

FIG. 56 is a flowchart for explaining an optical sensor packagemanufacturing process according to a fourteenth embodiment of thepresent invention.

FIG. 57-1 is a schematic for explaining the optical sensor packagemanufacturing process according to the fourteenth embodiment.

FIG. 57-2 is a schematic for explaining the optical sensor packagemanufacturing process according to the fourteenth embodiment.

FIG. 57-3 is a schematic for explaining the optical sensor packagemanufacturing process according to the fourteenth embodiment.

FIG. 57-4 is a schematic for explaining the optical sensor packagemanufacturing process according to the fourteenth embodiment.

FIG. 57-5 is a schematic for explaining the optical sensor packagemanufacturing process according to the fourteenth embodiment.

FIG. 57-6 is a schematic for explaining the optical sensor packagemanufacturing process according to the fourteenth embodiment.

FIG. 58 is a plan view for explaining an aperture in the optical sensoraccording to the fourteenth embodiment.

FIG. 59-1 is a schematic for explaining the optical sensor packagemanufacturing process according to the fourteenth embodiment.

FIG. 59-2 is a schematic for explaining the optical sensor packagemanufacturing process according to the fourteenth embodiment.

FIG. 59-3 is a schematic for explaining the optical sensor packagemanufacturing process according to the fourteenth embodiment.

FIG. 59-4 is a schematic for explaining the optical sensor packagemanufacturing process according to the fourteenth embodiment.

FIG. 59-5 is a schematic for explaining the optical sensor packagemanufacturing process according to the fourteenth embodiment.

FIG. 59-6 is a schematic for explaining the optical sensor packagemanufacturing process according to the fourteenth embodiment.

FIG. 60 is a plan view for explaining a light source according to afifteenth embodiment of the present invention.

FIG. 61 is a plan view for explaining a light emitting portion of thelight source according to the fifteenth embodiment.

FIG. 62 is a plan view for explaining an exemplary modification of thelight source according to the fifteenth embodiment.

FIG. 63 is a plan view for explaining another exemplary modification ofthe light source according to the fifteenth embodiment.

FIG. 64 is a plan view for explaining a waveguide for guiding the lightfrom the light source according to the fifteenth embodiment.

FIG. 65 is a plan view for explaining a waveguide for guiding the lightfrom the light source according to the fifteenth embodiment.

FIG. 66 is a plan view for explaining a waveguide for guiding the lightfrom the light source according to the fifteenth embodiment.

FIG. 67 is a plan view for explaining a waveguide for guiding the lightfrom the light source according to the fifteenth embodiment.

FIG. 68 is a flowchart for explaining a light source packagemanufacturing process according to the fifteenth embodiment.

FIG. 69-1 is a schematic for explaining the light source packagemanufacturing process according to the fifteenth embodiment.

FIG. 69-2 is a schematic for explaining the light source packagemanufacturing process according to the fifteenth embodiment.

FIG. 69-3 is a schematic for explaining the light source packagemanufacturing process according to the fifteenth embodiment.

FIG. 69-4 is a schematic for explaining the light source packagemanufacturing process according to the fifteenth embodiment.

FIG. 69-5 is a schematic for explaining the light source packagemanufacturing process according to the fifteenth embodiment.

FIG. 69-6 is a schematic for explaining the light source packagemanufacturing process according to the fifteenth embodiment.

FIG. 70 is a schematic for explaining shielding of the light sourceaccording to the fifteenth embodiment.

FIG. 71 is a schematic for explaining a light source with a highershielding efficiency according to the fifteenth embodiment.

FIG. 72 is a schematic for explaining a light source with a highershielding efficiency according to the fifteenth embodiment.

FIG. 73 is a flowchart for explaining an optical scale manufacturingprocess according to a sixteenth embodiment of the present invention.

FIG. 74-1 is a schematic for explaining the optical scale manufacturingprocess according to the sixteenth embodiment.

FIG. 74-2 is a schematic for explaining the optical scale manufacturingprocess according to the sixteenth embodiment.

FIG. 74-3 is a schematic for explaining the optical scale manufacturingprocess according to the sixteenth embodiment.

FIG. 74-4 is a schematic for explaining the optical scale manufacturingprocess according to the sixteenth embodiment.

FIG. 74-5 is a schematic for explaining the optical scale manufacturingprocess according to the sixteenth embodiment.

FIG. 74-6 is a schematic for explaining the optical scale manufacturingprocess according to the sixteenth embodiment.

FIG. 74-7 is a schematic for explaining the optical scale manufacturingprocess according to the sixteenth embodiment.

FIG. 75 is a flowchart for explaining an optical scale manufacturingprocess according to a seventeenth embodiment of the present invention.

FIG. 76-1 is a schematic for explaining the optical scale manufacturingprocess according to the seventeenth embodiment.

FIG. 76-2 is a schematic for explaining the optical scale manufacturingprocess according to the seventeenth embodiment.

FIG. 76-3 is a schematic for explaining the optical scale manufacturingprocess according to the seventeenth embodiment.

FIG. 76-4 is a schematic for explaining the optical scale manufacturingprocess according to the seventeenth embodiment.

FIG. 76-5 is a schematic for explaining the optical scale manufacturingprocess according to the seventeenth embodiment.

FIG. 76-6 is a schematic for explaining the optical scale manufacturingprocess according to the seventeenth embodiment.

FIG. 77 is a schematic for explaining an example of a wire grid patternon the optical scale according to the seventeenth embodiment.

FIG. 78 is a schematic for explaining an example of the wire gridpattern on the optical scale according to the seventeenth embodiment.

FIG. 79 is a schematic for explaining an example of the wire gridpattern on the optical scale according to the seventeenth embodiment.

FIG. 80 is a schematic for explaining an example of the wire gridpattern on the optical scale according to the seventeenth embodiment.

FIG. 81 is a schematic for explaining an example of the wire gridpattern on the optical scale according to the seventeenth embodiment.

FIG. 82 is a schematic for explaining an example of the wire gridpattern on the optical scale according to the seventeenth embodiment.

FIG. 83 is a schematic for explaining an example of the wire gridpattern on the optical scale according to the seventeenth embodiment.

FIG. 84 is a schematic for explaining an example of the wire gridpattern on the optical scale according to the seventeenth embodiment.

FIG. 85 is a schematic for explaining an example of the wire gridpattern on the optical scale according to the seventeenth embodiment.

FIG. 86 is a schematic for explaining an example of the wire gridpattern on the optical scale according to the seventeenth embodiment.

FIG. 87 is a schematic for explaining an optical scale according to aneighteenth embodiment of the present invention.

FIG. 88 is a schematic for explaining the polarizing axes in the opticalsensor according to the eighteenth embodiment.

FIG. 89 is a schematic for explaining the polarizing axes in the opticalsensor according to the eighteenth embodiment.

FIG. 90 is a schematic for explaining the polarizing axes in the opticalsensor according to the eighteenth embodiment.

FIG. 91 is a schematic for explaining an exemplary modification of theoptical scale according to the eighteenth embodiment.

FIG. 92 is a schematic for explaining an exemplary modification of theoptical sensor according to the eighteenth embodiment.

FIG. 93 is a schematic for explaining outputs from the encoder accordingto the eighteenth embodiment.

FIG. 94 is a schematic for explaining an optical scale according to anineteenth embodiment of the present invention.

FIG. 95 is a schematic for explaining polarizing axes of the opticalsensor according to the nineteenth embodiment.

FIG. 96 is a schematic for explaining the polarizing axes of the opticalsensor according to the nineteenth embodiment.

FIG. 97 is a schematic for explaining outputs from the encoder accordingto the nineteenth embodiment.

FIG. 98 is a schematic for explaining outputs from the encoder accordingto the nineteenth embodiment.

FIG. 99 is a schematic for explaining an exemplary modification of theencoder according to the nineteenth embodiment.

FIG. 100 is a schematic for explaining an optical sensor in the encoderillustrated in FIG. 99.

FIG. 101 is a schematic for explaining the optical sensor in the encoderillustrated in FIG. 99.

FIG. 102 is a schematic for explaining an exemplary modification of theencoder according to the nineteenth embodiment.

FIG. 103 is a schematic for explaining an arrangement of the opticalsensors in the encoder illustrated in FIG. 102.

FIG. 104 is a block diagram of the encoder according to the nineteenthembodiment.

FIG. 105 is a block diagram of the encoder according to the nineteenthembodiment.

FIG. 106 is a schematic for explaining angle detection signal outputsfrom the encoder according to the nineteenth embodiment.

FIG. 107 is a schematic for explaining the angle detection signaloutputs from the encoder according to the nineteenth embodiment.

FIG. 108 is a schematic for explaining the angle detection signaloutputs from the encoder according to the nineteenth embodiment.

FIG. 109 is a schematic for explaining the angle detection signaloutputs from the encoder according to the nineteenth embodiment.

FIG. 110 is a flowchart for explaining the angle detection signaloutputs from the encoder according to the nineteenth embodiment.

FIG. 111 is a schematic for explaining an optical scale according to atwentieth embodiment of the present invention.

FIG. 112 is a schematic for explaining a relation between a rotationangle and an angle range in the optical scale according to the twentiethembodiment.

FIG. 113-1 is a schematic for explaining an optical scale according to atwenty-first embodiment of the present invention.

FIG. 113-2 is a schematic for explaining the optical scale according tothe twenty-first embodiment.

FIG. 114-1 is a schematic for explaining a relation between a rotationangle and a Lissajous angle in the optical scales according to thetwenty-first embodiment.

FIG. 114-2 is a schematic for explaining a relation between a rotationangle and a Lissajous angle in the optical scale according to thetwenty-first embodiment.

FIG. 114-3 is a schematic for explaining a relation between a rotationangle and a Lissajous angle in the optical scale according to thetwenty-first embodiment.

FIG. 114-4 is a schematic for explaining a relation between a rotationangle and a Lissajous angle in the optical scale according to thetwenty-first embodiment.

FIG. 115-1 is a schematic for explaining a relation between a rotationangle and a Lissajous angle in the optical scale according to thetwenty-first embodiment.

FIG. 115-2 is a schematic for explaining a relation between a rotationangle and a Lissajous angle in the optical scale according to thetwenty-first embodiment.

FIG. 115-3 is a schematic for explaining a relation between a rotationangle and a Lissajous angle in the optical scale according to thetwenty-first embodiment.

FIG. 115-4 is a schematic for explaining a relation between a rotationangle and a Lissajous angle in the optical scale according to thetwenty-first embodiment.

FIG. 116-1 is a schematic for explaining a relation between a rotationangle and a Lissajous angle in the optical scale according to thetwenty-first embodiment.

FIG. 116-2 is a schematic for explaining a relation between a rotationangle and a Lissajous angle in the optical scale according to thetwenty-first embodiment.

FIG. 116-3 is a schematic for explaining a relation between a rotationangle and a Lissajous angle in the optical scale according to thetwenty-first embodiment.

FIG. 116-4 is a schematic for explaining a relation between a rotationangle and a Lissajous angle in the optical scale according to thetwenty-first embodiment.

FIG. 117-1 is a schematic for explaining a relation between a rotationangle and a Lissajous angle in the optical scale according to thetwenty-first embodiment.

FIG. 117-2 is a schematic for explaining a relation between a rotationangle and a Lissajous angle in the optical scale according to thetwenty-first embodiment.

FIG. 117-3 is a schematic for explaining a relation between a rotationangle and a Lissajous angle in the optical scale according to thetwenty-first embodiment.

FIG. 117-4 is a schematic for explaining a relation between a rotationangle and a Lissajous angle in the optical scale according to thetwenty-first embodiment.

FIG. 118-1 is a schematic for explaining a relation between a rotationangle and a Lissajous angle in the optical scale according to thetwenty-first embodiment.

FIG. 118-2 is a schematic for explaining a relation between a rotationangle and a Lissajous angle in the optical scale according to thetwenty-first embodiment.

FIG. 118-3 is a schematic for explaining a relation between a rotationangle and a Lissajous angle in the optical scale according to thetwenty-first embodiment.

FIG. 118-4 is a schematic for explaining a relation between a rotationangle and a Lissajous angle in the optical scale according to thetwenty-first embodiment.

FIG. 119-1 is a schematic for explaining a relation between a rotationangle and a Lissajous angle in an optical scale according to acomparative example;

FIG. 119-2 is a schematic for explaining a relation between a rotationangle and a Lissajous angle in the optical scale according to thecomparative example;

FIG. 119-3 is a schematic for explaining a relation between a rotationangle and a Lissajous angle in the optical scale according to thecomparative example;

FIG. 119-4 is a schematic for explaining a relation between a rotationangle and a Lissajous angle in the optical scale according to thecomparative example.

FIG. 120 is a flowchart for explaining an operation of a torquedetection apparatus according to a twenty-second embodiment of thepresent invention.

DESCRIPTION OF EMBODIMENTS

Embodiments of the present invention will now be explained in detailwith reference to some drawings. The descriptions in the followingembodiments are not intended to limit the scope of the present inventionin any way. The elements described hereunder include those that can beeasily thought of by those skilled in the art and substantially the sameelements. The elements described hereunder may also be combined asappropriate.

First Embodiment

FIG. 1 is a schematic of a structure of an encoder unit according to afirst embodiment of the present invention. This encoder unit 1 includesa shaft 29 connected to a rotary machine such as a motor, a stator 20, arotor 10, and an optical sensor package 31 in which an optical sensor,which is described later, capable of reading a signal pattern ispackaged.

The rotor 10 has an optical scale 11 that is a disk-shaped member. Theoptical scale 11 is made of silicon, glass, or a polymer material, forexample. The optical scale 11 has signal tracks T1 on one or both of thedisk surfaces. The shaft 29 is mounted on the opposite surface of therotor 10 on which the optical scale 11 is mounted.

The stator 20 is fixed independently of the shaft 29 and the rotor 10.The stator 20 has a bearing 21. The stator 20 supports the shaft 29rotatably via the bearing 21. When the shaft 29 is rotated by therotation of the motor, the rotor 10 is caused to rotate in associationwith the shaft 29 about a center O as an axial center. The opticalsensor package 31 is fixed to the stator 20 via a housing. When therotor 10 is rotated, the signal tracks T1 on the optical scale 11 moverelatively to the optical sensor package 31.

FIG. 2-1 is a schematic for explaining an arrangement of the opticalscale and the optical sensor. When the rotor 10 described above isrotated, the signal tracks T1 on the optical scale 11 move relatively tothe optical sensor package 31 in a direction R, for example. The opticalsensor package 31 includes an optical sensor 35 capable of reading thesignal tracks T1 on the optical scale 11 and a light source 41. Thelight source light 71 from the light source 41 is reflected on thesignal tracks T1 on the optical scale 11, and the optical sensor 35detects the reflected light 72 thus reflected as incident light. Theencoder unit 1 according to the first embodiment may include anarrangement of a transmissive optical scale and optical sensor, withoutlimitation to that of the reflective optical scale and the opticalsensor described above.

FIG. 2-2 is a schematic for explaining an exemplary modification of thearrangement of the optical scale and the optical sensor. When the rotor10 is rotated, the signal tracks T1 on the optical scale 11 moverelatively to the optical sensor package 31 in the direction R, forexample. As illustrated in FIG. 2-2, in the transmissive modification,the optical sensor package 31 includes the optical sensor 35 capable ofreading the signal tracks T1 on the optical scale 11. The light source41 is arranged at a position facing the optical sensor 35 across theoptical scale 11. With this structure, the light source light 71 fromthe light source 41 is passed through the signal tracks T1 on theoptical scale 11, and the optical sensor 35 detects a transmissive light73 thus passed through as the incident light.

FIG. 3 is a block diagram of the encoder according to the firstembodiment. An encoder 2 includes the encoder unit 1 and a computingunit 3. As illustrated in FIG. 3, the optical sensor 35 included in theencoder unit 1 is connected to the computing unit 3. The computing unit3 is connected to a control unit 5 of the rotary machine such as amotor.

The encoder 2 uses the optical sensor 35 to detect the reflected light72 or the transmissive light 73 which is the light source light 71passed through or reflected on the optical scale 11 and becomingincident on the optical sensor 35. The computing unit 3 computes arelative position of the rotor 10 included in the encoder unit 1 withrespect to the optical sensor package 31, from the detection signal fromthe optical sensor 35. The computing unit 3 then outputs the informationof the relative position to the control unit 5 of the rotary machinesuch as a motor as a control signal.

The computing unit 3 is a computer such as a personal computer (PC), andincludes an input interface 4 a, an output interface 4 b, a centralprocessing unit (CPU) 4 c, a read-only memory (ROM) 4 d, a random accessmemory (RAM) 4 e, and an internal storage device 4 f. The inputinterface 4 a, the output interface 4 b, the CPU 4 c, the ROM 4 d, theRAM 4 e, and the internal storage device 4 f are connected via aninternal bus. The computing unit 3 may be configured as a dedicatedprocessing circuit.

The input interface 4 a receives an input signal from the optical sensor35 included in the encoder unit 1, and outputs the input signal to theCPU 4 c. The output interface 4 b receives a control signal from the CPU4 c, and outputs the control signal to the control unit 5.

The ROM 4 d stores therein computer programs such as a basicinput/output system (BIOS). The internal storage device 4 f is a harddisk drive (HDD) or a flash memory, for example, and stores therein anoperating system program and application programs. The CPU 4 cimplements various functions by executing the computer programs storedin the ROM 4 d or in the internal storage device 4 f, using the RAM 4 eas a working area.

The internal storage device 4 f stores therein a database in which apolarization axis of the optical scale 11, which is described later, isassociated with an output of the optical sensor 35.

FIG. 4 is a schematic for explaining an example of a wire grid patternon the optical scale according to the first embodiment. The signaltracks T1 illustrated in FIG. 4 is made of an arrangement of wires g,which is referred to as a wire grid pattern, formed on the optical scale11 illustrated in FIG. 1.

The wire g is arranged in plurality, in such a manner that the wires donot intersect with one another, and in such a manner that each of thetangential directions of the respective wires changes continuously.Provided between the adjacent wires g is a transmissive area w throughwhich the entire or a part of the light source light 71 is allowed topass. When the width of the wire g and the pitch between the adjacentwires g, that is, the width of the wire g and the width of thetransmissive area w, are made sufficiently smaller than the wavelengthof the light source light 71 from the light source 41, the optical scale11 can polarize the reflected light 72 or the transmissive light 73 ofthe light source light 71.

This structure allows the polarization of the transmissive light 73 orthe reflected light 72 to change correspondingly to the tangentialdirections of the respective wires, which are dependent on the positionwhere the light source light 71 output to the optical scale 11 is passedthrough or is reflected. Therefore, the optical scale 11 does not needto be provided with highly granular segments each having a differentpolarizing direction. As a result, the optical scale 11 allows a highresolution to be achieved even when the size of the optical scale isreduced. When the size of the optical scale 11 is reduced, thearrangement of the light source 41 and the optical sensor 35 can bedesigned more freely. Furthermore, the optical scale 11 can have ahigher heat resistance than that of a photo-induced polarizer. Becausethe optical scale 11 has a line pattern without any intersections evenlocally, a highly accurate optical scale with a smaller error can beachieved. Furthermore, because the optical scale 11 can be stablymanufactured through a bulk-exposure or nanoimprinting, highly accurateoptical scales with small error can be achieved.

FIG. 5 is a schematic for explaining an example of the wire patternaccording to the first embodiment. As the wires g, the patternillustrated in FIG. 5 is arranged in plurality at different distancesfrom the coordinates (0, 0), but arranged so that the tangentialdirections of the respective wires g are orientated the same. Each ofsuch patterns is cut out as a donut-like shape, as illustrated in FIG.4. FIGS. 6 and 7 are schematics for explaining a relation between arotation angle and a polarization axis direction in the optical scaleaccording to the first embodiment. In FIG. 6, θrot denotes a rotationangle, and θd denotes a change in an angle of the tangent on the wirewith respect to the moving radius direction, that is, a change in anangle of the tangent line TGL along the tangential direction detected bythe optical sensor package 31. When the rotation angle is 360 degrees,that is, when the signal tracks T1 are rotated once, θd changes asillustrated in FIG. 7. In the pattern of the wire g illustrated in FIG.5, for example, when the rotation angle θrot changes from 0 degrees to15 degrees, the tangential angle θd changes from 90 degrees to 45degrees. In the same manner, for example, when the rotation angle θrotchanges from 15 degrees to 30 degrees, the tangential angle θd changesfrom 45 degrees to 90 degrees. In this manner, the optical scale 11allows the tangential angle θd to change in a cyclic manner,correspondingly to the rotation angle θrot. As illustrated in FIG. 7, ajump in the tangential angle θd occurs every time there is a 30-degreechange in the rotation angle θrot. The computing unit 3 can handle suchtangential angles θd corresponding to every 30-degree change in therotation angle θrot as the same tangential direction (polarizationaxis). Explained so far is an example in which the amount of the changein the tangential angle θd is 45 degrees, but the embodiment is notlimited thereto, and the amount of the change in the tangential angle θdmay be less than 45 degrees, for example.

FIGS. 8-1, 8-2, 9-1, 9-2, 10-1, and 10-2 are schematics for explainingthe wire grid pattern on the optical scale according to the firstembodiment. In the wire grid pattern according to the embodiment, toallow a polarization axis to be detected based on θd which is thetangential angle, adjacent wires g1 and g2 are changed continuouslywhile maintaining the same tangential angle. As illustrated in FIGS. 8-1and 9-1, the wire grid pattern according to the embodiment is providedin such a manner that the width Δw1 and the width Δw2 of thetransmissive area are different between positions where the tangentialdirections are different.

For example, the width Δw1 of the transmissive area where the adjacentwires g1 and g2 are curved, as illustrated in FIG. 8-1, is set widerthan the width Δw2 of the transmissive area illustrated in FIG. 9-1.Such a configuration allows a plurality of wires to be arranged easilyin a manner allowing each of the tangential directions to changecontinuously. The adjacent wires g1 and g2 form a wire grid patternillustrated in FIG. 10-1. By arranging the adjacent wires g at the sameregularity, the signal tracks T1 forming the wire grid patternillustrated in FIG. 4 can be achieved.

In the wire grid pattern according to the embodiment illustrated inFIGS. 8-2 and 9-2, the center line of each of the wires g illustrated inFIG. 4 is indicated. In the wire grid pattern according to theembodiment, to allow a polarization axis to be detected based on θdwhich is the tangential angle, the adjacent wires g1 and g2 are changedcontinuously while maintaining the same tangential angle. In the wiregrid pattern, the adjacent wires g2 and g3 are also changed continuouslywhile maintaining the same tangential angle. The reference point of thetangential angle of the wires g1, g2, and g3 is the center O of therotor 10 (the position corresponding to (0, 0) in FIG. 5), as mentionedearlier.

As illustrated in FIG. 8-2, the pitch Δw1 (interval) between the centerlines of the adjacent wires g1 and g2 in the radial direction is thesame as the pitch Δw1 between the center lines of the adjacent wires g2and g3. As illustrated in FIG. 9-2, the pitch Δw2 between the centerlines of the adjacent wires g1 and g2 in the radial direction is thesame as the pitch Δw2 between the center lines of the adjacent wires g2and g3. This configuration allows the wire g1, the wire g2, and the wireg3 to have the same tangential angle with respect to the same radialdirection of the wire g1, the wire g2, and the wire g3.

The wires g1, g2, and g3 are arranged in a manner not intersecting oneanother, and in such a manner that each of the tangential directionschanges continuously. As a result, at the positions where the tangentialangles are oriented differently (at positions of different radialdirections), the wires g1, g2, and g3 are arranged so that the pitch Δw1illustrated in FIG. 8-2 becomes different from the pitch Δw2 illustratedin FIG. 9-2, for example. For example, the pitch Δw1 in the area wherethe adjacent wires g1 and g2 are curved (wound), as illustrated in FIG.8-2, is set wider than the pitch Δw2 illustrated in FIG. 9-2. In thismanner, the tangential directions of the respective adjacent wires g1,g2, and g3 are oriented the same between areas where the respectivepitches Δw1 (interval) between the wires are the same, while thetangential directions on the wires g1, g2, and g3 are orienteddifferently between the areas where the respective pitches Δw2(interval) and pitch Δw1 (interval) are different. Such a configurationallows a plurality of wires to be arranged easily in a manner allowingeach of the tangential directions to change continuously.

The pitch of the wires may be defined as an interval between the edgesof the adjacent wires g1 and g2, as illustrated in FIG. 10-2. Along thesame radial direction, the pitch (interval) Δw3 between edges of theadjacent wires g1 and g2 remains the same as the pitch Δw3 between theedges of the adjacent wires g2 and g3. Along the radial direction, thepitch Δw4 between the edges of the adjacent wires g1 and g2 remains thesame as the pitch Δw4 between the edges of the adjacent wires g2 and g3.In this manner, along the same radial direction across the wires g1, g2,and g3, the tangential angles of the respective wires g1, g2, and g3 arekept the same.

The wires g1, g2, and g3 are arranged in a manner not intersecting oneanother, and in such a manner that each of the tangential directionschanges continuously. As a result, the wire grid pattern according tothe embodiment is arrangement in such a manner that, the pitch Δw3 andthe pitch Δw4 illustrated in FIG. 10-2, for example, are differentbetween the areas where the tangential angles of the wires aredifferent. The pitch Δw3 as illustrated in FIG. 10-2 in the area wherethe adjacent wires g1 and g2 are curved (wound) is set wider than thepitch Δw4 in the area where the wires g1 and g2 are linear. Such aconfiguration allows a plurality of wires to be arranged easily in amanner allowing each of the tangential directions to changecontinuously.

As explained above, by arranging the wires g1, g2, and g3 at the sameregularity, the signal tracks T1 having the wire grid patternillustrated in FIG. 4 can be achieved. Each of the wires g illustratedin FIG. 4 is based on a closed curve, and is arranged so that the pitch(interval) of the adjacent wires g remains the same along the sameradial direction with the reference point at the center O. Furthermore,because each of the wires g on the optical scale 11 can be manufacturedas a continuous pattern, the optical scale 11 can be formed using asimple line-and-space pattern. Therefore, accuracy of thephotolithography process, for example, can be improved. As a result, theoptical scale 11 can be produced as a highly accurate scale.Furthermore, when the wires g are arranged to have an equal pitch(interval) between the adjacent wires g along the same radial directionwith a reference point at the center O, the pitch (interval) of theadjacent wires g, that is, the line-and-space ratio between the wiresg1, g2, and g3, may not be one to one, but changed as appropriatedepending on the positions, as long as such positions are at differentradial directions with the reference point at the center O. In thismanner, the optical scale 11 can correct the polarization ratio bychanging the line width ratio.

FIGS. 11-1, 11-2, 11-3, and 11-4 are schematics for explaining adetection area of the optical scale according to the first embodiment.In FIG. 11-1, the optical sensor 35 detects the polarization axis basedon the wire grid pattern of the signal tracks T1 in a sensing area C1.In FIG. 11-2, the optical sensor 35 detects the polarization axis basedon the wire grid pattern of the signal tracks T1 in a sensing area C2.The sensing area herein means an area where the light source light ispassed through or reflected on the optical scale 11.

As illustrated in FIGS. 11-1 and 11-2, as the optical scale 11 isrotated in the direction R, the sensing area of the signal tracks T1 onthe optical scale is changed. As mentioned earlier, a plurality of wiresare arranged in such a manner that each of the tangential directionschanges continuously, as the signal tracks T1 on the optical scale 11.In other words, as mentioned earlier, in the sensing area C1, theadjacent wires g of the signal tracks T1 are arranged at an equalinterval. In the sensing area C2 as well, the adjacent wires g arearranged at an equal interval.

The interval between the adjacent wires g in the sensing area C1 may bedifferent from that in the sensing area C2. In other words, theintervals between the adjacent wires g are different at the positionswhere the tangential directions are oriented differently. The lightsource light 71 output to the wires g becomes the reflected light 72 orthe transmissive light 73 having its polarization axis changedcorrespondingly to the tangential direction of the wires g.

FIG. 11-3 indicates that the direction P90 of the pattern in the sensingarea C1 illustrated in FIG. 11-1 is +90 degrees, for example. FIG. 11-4indicates that the direction P45 of the pattern in the sensing area C2illustrated in FIG. 11-2 is +45 degrees. The polarization axis of theincident light that is incident on the optical sensor 35 changes as theoptical scale 11 is rotated, because the tangential angle of the wiregrid pattern changes. Therefore, the rotation of the optical scale 11can be recognized by detecting a change in the polarization axis.Explained now is the optical sensor 35 according to the first embodimentserving as a polarization splitting unit by detecting a change in thepolarization axis.

FIGS. 12-1 and 12-2 are schematics for explaining the optical sensoraccording to the first embodiment. As illustrated in FIG. 12-1, theoptical sensor 35 includes a first optical sensor 36A and a secondoptical sensor 36B. The first optical sensor 36A includes a firstpolarizing layer that splits incident light into light with a firstpolarization direction, and a first photoreceiver for receiving firstpolarized light split by the first polarizing layer, and is capable ofdetecting the intensity of light with the first polarization direction.The second optical sensor 36B includes a second polarizing layer thatsplits the incident light into light with a second polarizationdirection, and a second photoreceiver for receiving second polarizedlight split by the second polarizing layer, and is capable of detectingthe intensity of light with the second polarization direction.

This structure enables the incident light to split into the firstpolarized light and the second polarized light. As a result, thecomputing unit 3 can calculate the polarization angle of the reflectedlight 72 or the transmissive light 73 based on signal intensities of thepolarized component having the first polarization direction and of thepolarized component having the second polarization direction thus split.The first polarization direction and the second polarization directionare preferably different from each other by 90 degrees to allow thecomputing unit 3 to calculate the polarization angle easily.

As illustrated in FIG. 12-2, the first optical sensor 36A and the secondoptical sensor 36B may be arranged alternatingly in the vertical and thehorizontal directions on the optical sensor 35. With this configuration,even when a foreign substance blocks a part of the sensing area, thechances of the first optical sensor 36A and the second optical sensor36B being blocked by approximately the same degree can be increased, sothat the possibility of the signal intensity output from one of thesesensors dropping extremely can be reduced. Therefore, even when theintensity of the incident light is decreased by a foreign substance, theencoder 2 can detect a change in the polarization direction via adifferential signal V, which is described later, in a manner lessaffected by foreign substances.

FIGS. 13-1, 13-2, and 13-3 are schematics for explaining splitting ofincident light into polarized components in the optical sensor accordingto the first embodiment. As illustrated in FIG. 13-1, the light sourcelight 71 polarized to a polarization direction Pm by the optical scale11 becomes incident on a sensing area Tm of the optical sensor 35. InFIG. 13-1, a foreign substance D1 and a foreign substance D2 are presentin the sensing area Tm of the optical sensor 35. The polarizationdirection Pm of the incident light can be expressed by a signalintensity I(−) of the component having the first polarization directionand a signal intensity I(+) of the component having the secondpolarization direction. The first polarization direction and the secondpolarization direction are preferably different by 90 degrees, and thesecomponents are, for example, +45 degrees component and −45 degreescomponent with respect to a reference direction.

As illustrated in FIG. 13-2, the first optical sensor 36A detects thelight intensity passed through the first polarizing layer that splitsthe incident light to the light with the first polarization direction.Therefore, the first optical sensor 36A detects the signal intensityI(−) of the component with the first polarization direction. Asillustrated in FIG. 13-3, the second optical sensor 36B detects thelight intensity passed through the polarizing layer that splits theincident light to the light with the second polarization direction.Therefore, the second optical sensor 36B detects the signal intensityI(+) of the component having the second polarization direction.

The computing unit 3 illustrated in FIG. 3 acquires the signal intensityI(−) of the component having the first polarization direction and thesignal intensity I(+) of the component having the second polarizationdirection which are detection signals received from the optical sensor35. The computing unit 3 then calculates the differential signal V fromthe signal intensity I(−) of the component having the first polarizationdirection and the signal intensity I(+) of the component having thesecond polarization direction, following Equation (1) below.V=[I(+)−(−)]/[I(+)+I(−)]=sin(2θd)  (1)

Because the differential signal V calculated from Equation (1) does notinclude parameters affected by the light intensity of the light source41, the encoder 2 can reduce the influences of fluctuations such asthose in the distance between the optical sensor 35 and the opticalscale 11, and in the light intensity of the light source 41.Furthermore, even when the light intensity of the incident light isdecreased by foreign substances D1 and D2 as illustrated in FIG. 13-1,the encoder 2 can detect a change in the polarization direction Pm viathe differential signal V while suppressing the influence of the foreignsubstances D1 and D2.

FIG. 14 is a schematic for explaining a relation between a rotationangle and a differential signal in the optical sensor according to thefirst embodiment. The vertical axis in FIG. 14 represents thedifferential signal V, and the horizontal axis represents the rotationangle θrot illustrated in FIG. 6. When the rotation angle θrot reaches360 degrees, that is, when the optical scale 11 is rotated by once, thedifferential signal V indicates a waveform with six cycles. Thiswaveform matches the cycles of the curves in the wire patternillustrated in FIG. 5, which has a wave-like form with six cycles in the360 degrees. The waveform of the differential signal V illustrated inFIG. 14 is a sine wave, for example. The number of waves is merely anexample, and is not limited to the number of cycles described above.Although the differential signal V has different phases for thetransmissive light and for the reflected light, the differential signalV remains the same in having a waveform with six cycles.

The computing unit 3 stores information representing the relationbetween the rotation angle θrot and the differential signal Villustrated in FIG. 14 in at least one of the RAM 4 e and the internalstorage device 4 f, and the CPU 4 c can calculate the number ofrotations of the rotor 10 from information of the differential signal V.

For example, the computing unit 3 can calculate the tangential angle θdfrom the relation between the tangential angle θd and the rotation angleθrot illustrated in FIG. 7 and the differential signal V indicated inEquation (1) above. When the maximum angle θmax denotes a rotationalangle which is related to the number of wave-like forms (curves) on theoptical scale 11 of when the tangential angle θd is changed by themaximum degree, as illustrated in FIG. 7, a ratio of change in θd perθrot can be expressed as Equation (2) below.

$\begin{matrix}{\frac{{\mathbb{d}\theta}\; d}{{\mathbb{d}\theta}\;{rot}} = {\pm \frac{\left( {\pi/4} \right)}{\theta\;\max}}} & (2)\end{matrix}$

Information of the relation between the rotation angle θrot and thedifferential signal V can be acquired by substituting θd calculated fromEquation (2) in Equation (1). The computing unit 3 can then calculatethe rotation angle θrot from the differential signal V from thedetection signal of the optical sensor 35, based on the information ofthe relation between the rotation angle θrot and the differential signalV.

By providing the optical scale with the wire grid pattern in which thetangential angle θd and the maximum angle θmax of the tangential angleθd are changed by desired degrees, the encoder 2 can be a detectionapparatus with a relation between the rotation angle θrot and thedifferential signal V.

As described earlier, the encoder 2 includes the optical scale 11 isprovided with a plurality of wires arranged in a manner not intersectingone another, and in such a manner that each of the tangential directionschanges continuously. The optical sensor 35 also includes a firstpolarizing layer that splits incident light that is the light sourcelight 71 being incident from the light source 41 and passed through orreflected on the optical scale 11 to the light with a first polarizationdirection, the first optical sensor 36A for receiving the firstpolarized light split by the first polarizing layer, the secondpolarizing layer that splits the incident light into the light with thesecond polarization direction, and the second optical sensor 36B forreceiving the second polarized light split by the second polarizinglayer. The computing unit 3 serving as a computing unit then calculatesthe amount of relative movement between the optical scale 11 and theoptical sensor 35, from the intensity of the first polarized light andthe intensity of the second polarized light.

With this structure, the optical sensors detect the rotation angle ofthe rotor 10 using the polarizations of the transmissive light 73 or thereflected light 72 thus split. Therefore, the encoder 2 can reduce theinfluence of fluctuations in the amount of detected light caused byforeign substances or the like, compared with when the intensity of theincident light is directly detected. Because the tolerance of foreignsubstances is increased, the encoder can be used in an increased numberof environments.

Furthermore, the encoder 2 can reduce the influence of fluctuations inthe amount of detected light due to precisions in the optical path (thedistance from the optical scale to the optical sensor), even when usedis an optical encoder unit. As a result, the arrangement of the lightsources and the optical sensors can be designed more freely. In thismanner, the encoder unit 1 can be reduced in size. Furthermore, anoptical encoder can also achieve a higher resolution, compared with amagnetic encoder.

Modifications of Optical Sensor

FIGS. 15-1, 15-2, 15-3, and 16 are schematics for explaining exemplarymodifications of the optical sensor according to the first embodiment.The optical sensor 35 includes the first optical sensor 36A and thesecond optical sensor 36B. The first optical sensor 36A includes anelectrode base 36KA and first photoreceivers 36 a, and is capable ofdetecting the intensity of the light with the first polarizationdirection. Each of the first photoreceivers 36 a has a first polarizinglayer that splits incident light to the light with the firstpolarization direction, and receives first polarized light split by thefirst polarizing layer.

The second optical sensor 36B includes an electrode base 36KB and secondphotoreceivers 36 b, and is capable of detecting the intensity of lightwith a second polarization direction. Each of the second photoreceivers36 b has a second polarizing layer that splits incident light to lightwith the second polarization direction, and receives the secondpolarized light split by the second polarizing layer. As illustrated inFIG. 15-1, each of the first photoreceivers 36 a and the secondphotoreceivers 36 b is configured in a comb-like shape, engaging andspaced uniformly with each other. The electrode base 36KA and theelectrode base 36KB are both made of a conductive material such as gold(Au) or aluminum (Al) so that the electricity can be conducted to thefirst photoreceivers 36 a and the second photoreceivers 36 b. When theelectrode base 36KA and the electrode base 36KB are made of alight-shielding material, noise can be reduced.

Such a structure allows the incident light to be split into the firstpolarized light and the second polarized light. As a result, thecomputing unit 3 can calculate the polarization angle of the reflectedlight 72 or the transmissive light 73 based on the signal intensities ofthe polarized component having the first polarization direction and ofthe polarized component having the second polarization direction thussplit. The first polarization direction and the second polarizationdirection are preferably different from each other by 90 degrees toallow the computing unit 3 to calculate the polarization angle easily.

As illustrated in FIG. 15-2, the optical sensor 35 includes the firstoptical sensor 36A and the second optical sensor 36B. The first opticalsensor 36A includes the electrode base 36KA, a sensor base 36Kaconnected to the electrode base 36KA, and the first photoreceivers 36 a,and is capable of detecting the intensity of light with the firstpolarization direction. Each of the first photoreceivers 36 a has thefirst polarizing layer that splits incident light to the light with thefirst polarization direction, and receives the first polarized lightsplit by the first polarizing layer.

The second optical sensor 36B includes the electrode base 36KB, a sensorbase 36Kb connected to the electrode base 36KB, and the secondphotoreceivers 36 b, and is capable of detecting the intensity of lightwith the second polarization direction. Each of the secondphotoreceivers 36 b has the second polarizing layer that splits theincident light to the light with the second polarization direction, andreceives the second polarized light split by the second polarizinglayer. As illustrated in FIG. 15-2, each of the first photoreceivers 36a and the second photoreceivers 36 b is configured in a comb-like shape,engaging and spaced uniformly with each other. The electrode base 36KAand the electrode base 36KB are both made of a conductive material suchas Au or Al so that the electricity can be conducted to the firstphotoreceivers 36 a and the second photoreceivers 36 b.

The optical sensor 35 may also have an outer circumference following anarc shape, as illustrated in FIG. 15-3, without limitation to therectangular outer shape, which is illustrated in FIG. 15-1. For example,when the incident light that is incident to the optical sensor 35 iscircular, such first photoreceivers 36 a and second photoreceivers 36 bare allowed to receive the incident light by approximately the samedegree.

With such structures, even when a part of the sensing area is blocked bya foreign substance D3, as illustrated in FIG. 16, for example, thechances of the first photoreceivers 36 a and the second photoreceivers36 b being blocked by approximately the same degree can be increased, sothat the possibility of the signal intensity output from one of thefirst photoreceiver 36 a and the second photoreceiver 36 b droppingextremely can be reduced. Therefore, even when the intensity of theincident light is decreased by the foreign substance D3, the encoder 2can detect a change in the polarization direction Pm via thedifferential signal V, in a manner less affected by foreign substances.

Method for Manufacturing Optical Sensor

FIG. 17 is a flowchart for explaining an optical sensor manufacturingprocess according to the first embodiment. FIGS. 18-1 to 18-6 areschematics for explaining the optical sensor manufacturing processaccording to the first embodiment. FIGS. 18-1 to 18-6 are partialcross-sectional views for explaining the process of manufacturing theQ-Q cross section in FIG. 15-1. The method of manufacturing the opticalsensor will be explained with reference to FIGS. 15-1, 17, and 18-1 to18-6.

As illustrated in FIG. 17, to begin with, the manufacturing equipmentprepares an n-type silicon substrate 34, as illustrated in FIG. 18-1(Step S1). An n-type silicon substrate 34 is used as an example, butanother semiconductor substrate such as a gallium arsenide (GaAs)substrate may also be used instead of the n-type silicon substrate 34.The manufacturing equipment then performs a doping process in which thesilicon substrate 34 is doped with an element such as boron (B) orindium (In) (Step S2). As illustrated in FIG. 18-2, a P-typesemiconductor photoreceiver 37 is thus formed on the silicon substrate34.

As illustrated in FIG. 17, the manufacturing equipment then performs anetching process in which the silicon substrate 34 is masked with aphotoresist and etched so as to achieve the comb-like shape illustratedin FIG. 15-1 (Step S3). The etching may be physical etching or chemicaletching. As illustrated in FIG. 18-3, as a result of the etching,recesses 38 a are formed on the surface of the silicon substrate 34. Asa result of this process, the first optical sensor 36A and the secondoptical sensor 36B are separated, in the manner illustrated in FIG.15-1.

As illustrated in FIG. 17, the manufacturing equipment then performs aninsulating process in which the recesses 38 a are covered by aninsulating material such as SiO₂ or alumina via sputtering (Step S4). Asa result of this process, the recesses 38 a on the silicon substrate 34illustrated in FIG. 18-3 are filled with insulator 38 b, as illustratedin FIG. 18-4. In this insulating process, the surface is preferablysmoothed out so that the photoreceivers 37 become exposed.

As illustrated in FIG. 17, the manufacturing equipment performs a firstpolarizing layer forming process in which a first polarizing layer 39 ais formed at the positions corresponding to the first photoreceivers 36a illustrated in FIG. 15-1 (Step S5). The first polarizing layer 39 amay be formed using a photo-induced polarizing layer or a wire gridpattern in which wires are arranged in parallel, for example. In thismanner, the first polarizing layer 39 a is formed on every twophotoreceivers 37, as illustrated in FIG. 18-5.

As illustrated in FIG. 17, the manufacturing equipment then performs asecond polarizing layer forming process in which a second polarizinglayer 39 b is formed at positions corresponding to the secondphotoreceivers 36 b illustrated in FIG. 15-1 (Step S6). The secondpolarizing layer 39 b may be formed using a photo-induced polarizinglayer or a wire grid pattern in which wires are arranged in parallel,for example. In this manner, the second polarizing layer 39 b is formedon another every two photoreceivers 37, as illustrated in FIG. 18-6. Theelectrode base 36KA and the electrode base 36KB illustrated in FIG. 15-1are then formed using a conductive material such as Au or Al so that theelectricity can be conducted to the first photoreceivers 36 a and thesecond photoreceivers 36 b.

As illustrated in FIG. 18-6, the optical sensor 35 includes the firstphotoreceivers 36 a and the second photoreceivers 36 b each of which isconfigured in a comb-like shape, engaging and spaced uniformly with eachother. Each of the first photoreceivers 36 a has the first polarizinglayer 39 a for splitting incident light into the light with the firstpolarization direction so that the photodiode provided as a PN junctioncan receive the first polarized light split by the first polarizinglayer 39 a. Each of the second photoreceivers 36 b has the secondpolarizing layer 39 b for splitting the incident light to the light withthe second polarization direction so that the photodiode provided as aPN junction can receive the second polarized light split by the secondpolarizing layer 39 b. The photoreceivers are not limited to photodiodesformed as a PN junction, and phototransistors or the like may also beused. The photoreceiver may also be a photodiode formed with a pinjunction. Furthermore, the photoreceiver may be manufactured as anintegrated circuit in which an amplifier or peripheral circuitry isintegrated.

As explained above, the method for manufacturing an optical sensorincludes the photoreceiver forming process and the polarizing layerforming process. In the photoreceiver forming process, photoreceiversare formed on the surface of the silicon substrate 34 in such a mannerthat the first photoreceivers 36 a and the second photoreceivers 36 breceiving light are arranged alternatingly and spaced uniformly witheach other. In the polarizing layer forming process, the firstpolarizing layer 39 a that splits the incident light into the firstpolarized light with the first polarization direction is formed on topof the first photoreceivers 36 a so that the first polarized lightbecomes incident on the first photoreceivers 36 a, and the secondpolarizing layer 39 b splitting the incident light into the secondpolarized light with the second polarization direction is formed on topof the second photoreceivers so that the second polarized light becomesincident on the second photoreceivers 36 b.

Modification of Optical Scale

FIG. 19 is a schematic for explaining an exemplary modification of theoptical scale according to the first embodiment. On an optical scale 11a, the adjacent wires g are arranged linearly, in parallel with oneanother, as signal tracks T1 a. The optical scale 11 a according to themodification causes the polarization axis of the incident light that isincident on the optical sensor 35 to change in the rotatingcircumferential direction, as the optical scale 11 a is rotated. In thisembodiment, the optical scale 11 a may be made of an optical anisotropicmaterial in which the polarization axis of the incident light that isincident on the optical sensor 35 changes correspondingly to therotation of the optical scale 11 a.

As explained above, in the optical sensor 35 according to the firstembodiment, each of the first photoreceivers 36 a and the secondphotoreceivers 36 b is configured in a comb-like shape, engaging andspaced uniformly with each other. Each of the first photoreceivers 36 ahas the first polarizing layer 39 a that splits incident light into thelight with the first polarization direction so that the photodiodeprovided as a PN junction can receive the first polarized light split bythe first polarizing layer 39 a. Each of the second photoreceivers 36 bhas the second polarizing layer 39 b that splits the incident light tothe light with the second polarization direction so that the photodiodeprovided as a PN junction can receive the second polarized light splitby the second polarizing layer 39 b.

Such a structure allows the incident light that is the transmissivelight 73 or the reflected light 72 to be split into the first polarizedlight and the second polarized light. As a result, the computing unit 3serving as a computing unit can calculate the polarization angle of thetransmissive light 73 or the reflected light 72 from the signalintensities of the polarized components that are the first polarizedlight with the first polarization direction and the second polarizedlight with the second polarization direction thus split. Because thechances of the first photoreceivers 36 a and the second photoreceivers36 b being blocked by a foreign substance by approximately the samedegree can be increased, the possibility of the signal intensity outputfrom one of the first photoreceivers 36 a and the second photoreceivers36 b dropping extremely can be reduced. Therefore, even when theintensity of the incident light is decreased by a foreign substance, theoptical sensor 35 can detect a change in the polarization direction ofthe transmissive light 73 or the reflected light 72, in a manner lessaffected by foreign substances.

Modification of Encoder

FIG. 20 is a schematic of a structure of an encoder unit according to amodification of the first embodiment. The members that are the same asthose described above are assigned with the same reference numerals, andredundant explanations thereof are omitted hereunder. An encoder unit 1Aincludes the shaft 29 connected to the rotary machine such as a motor,the stator 20, the rotor 10, and an optical sensor package 31 and anoptical sensor package 32 both of which are capable of reading signalpatterns. The rotor 10 includes an optical scale 11 that is adisk-shaped member. The optical scale 11 has the signal tracks T1 andsignal tracks T2 on one or both of the disk surfaces.

The optical sensor package 32 has the same structure as the opticalsensor package 31, and is capable of reading the signal tracks T2. Thecomputing unit 3 can acquire the signal intensity I(−) of the componenthaving the first polarization direction and the signal intensity I(+) ofthe component having the second polarization direction that aredetection signals from the optical sensors 35 in the optical sensorpackages 31 and 32.

The signal tracks T2 are formed as the wire grid pattern described abovebut having a phase shifted from that of the signal tracks T1 by a givendegree, e.g., resulting in a differential signal V shifted by aone-quarter cycle from that of the signal tracks T1. When the rotor 10is rotated, the signal tracks T2 are rotated by the same rotation angleas the signal tracks T1. Therefore, the computing unit 3 can identify anabsolute position of the rotation angle of the rotor 10 by calculating aLissajous pattern from the differential signal from the signal tracks T2and the differential signal from the signal tracks T1. The encoder 2according to the modification can thus be an absolute encoder capable ofcalculating an absolute position of the rotor 10.

Second Embodiment

FIG. 21 is a schematic of a structure of an encoder unit according to asecond embodiment of the present invention. FIG. 22 is a side viewillustrating a structure of an encoder according to the secondembodiment. The members that are the same as those described above areassigned with the same reference numerals, and redundant explanationsthereof are omitted hereunder. This encoder unit 1B includes a rotor 10Aserving as a shaft connected to a rotary machine such as a motor, astator 20A, and an optical sensor package 31A capable of reading signalpatterns. The stator 20A is fixed independently of the rotor 10A.

The rotor 10A is a cylindrical member. On the outer circumferentialsurface of the cylindrical rotor 10A, an optical scale 11A is provided.The optical scale 11A has signal tracks T11 that are a wire gridpattern. The optical sensor package 31A is fixed via the stator 20A.When the rotor 10A is rotated in an R1 direction, the signal tracks T11on the optical scale 11A move relatively to the optical sensor package31A.

The optical sensor package 31A includes an optical sensor 35A capable ofreading the signal tracks T11 on the optical scale 11A, and a lightsource 41A. The light source light 71 from the light source 41A isreflected on the signal tracks T11 on the optical scale 11A, andreflected light 72 thus reflected is detected by the optical sensor 35Aas incident light. The optical sensor 35A is the same as the opticalsensor 35 described above. The light source 41A is the same as the lightsource 41 described above. The encoder according to the embodimentincludes the encoder unit 1B and the computing unit 3, and the opticalsensor 35A in the encoder unit 1B is connected to the computing unit 3,in the same manner as illustrated in FIG. 3. The computing unit 3 isconnected to the control unit 5 of the rotary machine such as a motor.

FIG. 23 is a schematic for explaining an example of the wire gridpattern on the optical scale according to the second embodiment. Anarrangement of wires g, which is referred to as a wire grid pattern,illustrated in FIG. 23 is formed on the optical scale 11A illustrated inFIGS. 21 and 22 as the signal tracks T11. Provided between the adjacentwires g is a transmissive area w through which the entire or a part ofthe light source light 71 is allowed to pass. When the width of the wireg and the pitch between the adjacent wires g, that is, the width of thewire g and the width of the transmissive area w are made sufficientlysmaller than the wavelength of the light source light 71 from the lightsource 41A, the optical scale 11A can polarize the reflected light 72 ofthe light source light 71. When the rotor 10A is rotated, for example,the sensing area Ls1 of the optical sensor package 31A moves to thesensing area Ls2.

FIGS. 24-1, 24-2, 25-1, and 25-2 are schematics for explaining the wiregrid pattern on the optical scale according to the second embodiment. Toallow the polarization axis to be detected based on θs which is thetangential angle, adjacent wires g3 and g4 in the wire grid patternaccording to the embodiment are changed continuously while keeping thesame tangential angle. The adjacent wires g3 and g4 are arranged to havedifferent transmissive area width Δw3 and width Δw4 in the areas wherethe tangential angles θs are different. For example, the transmissivearea width Δw3 in the area where the adjacent wires g3 and g4 are curvedis set wider than the transmissive area width Δw4. In this manner, awire grid pattern such as that illustrated in FIG. 25-1 is achieved. Byarranging the wire grid pattern at the same regularity, the signaltracks T11 having the wire grid pattern illustrated in FIG. 23 can beachieved on the optical scale 11A. The tangential angle θs is an angleformed by a direction in parallel with the R1 direction illustrated inFIG. 21, that is, a horizontal line HZL representing the direction ofthe movement, and the tangent line TGL.

FIG. 24-2 is a schematic for explaining the wire grid pattern on theoptical scale according to the second embodiment. In the wire gridpattern according to the embodiment illustrated in FIG. 24-2, the centerline of each of the wires g in FIG. 23 is indicated. To allow θs that isthe tangential angle to be detected as a polarization axis, adjacentwires g4 and g5 in the wire grid pattern according to the embodiment arechanged continuously while maintaining the same tangential angle. In thewire grid pattern, adjacent wires g5 and g6 are also changedcontinuously while maintaining the same tangential angle. The wires g4,g5, and g6 are arranged in a manner having a given intervaltherebetween, or in a manner offset from each other in a directionperpendicular to the direction in which the sensing area Ls1 moves tothe sensing area Ls2 (in the vertical directions in FIG. 23).

In the sensing area Ls1 illustrated in FIG. 23, the pitch (interval) Δw1between the center lines of the respective adjacent wires g4 and g5illustrated in FIG. 24-2 is the same as the pitch Δw1 between the centerlines of the respective adjacent wires g5 and g6. Similarly, in thesensing area Ls2 illustrated in FIG. 23, the pitch ΔW2 between thecenter lines of the respective adjacent wires g4 and g5 illustrated inFIG. 24-2 is the same as the pitch ΔW2 between the center lines of therespective adjacent wires g5 and g6. Therefore, the same tangentialangle is retained among the wires g4, g5, and g6, in each of the sensingarea Ls1 and the sensing area Ls2.

The wires g4, g5, and g6 are arranged in a manner not intersecting oneanother, and in such a manner that each of the tangential directionschanges continuously. As a result, the wire grid pattern according tothe embodiment is arranged in such a manner that the pitches Δw1 and thepitches ΔW2 illustrated in FIG. 24-2 are different between the areaswhere the tangential angles are different, for example. For example, thepitch ΔW2 in the area where the adjacent wires g4 and g5 are curved(wound) is set wider than the pitch Δw1 in the area where the wires g4and g5 are linear. Such a configuration allows a plurality of wires tobe arranged easily in a manner allowing each of the tangentialdirections to change continuously.

FIG. 25-2 is a schematic for explaining the wire grid pattern on theoptical scale according to the second embodiment. The pitch of the wiresmay be defined as an interval between the edges of the adjacent wires g4and g5, as illustrated in FIG. 25-2. In the sensing area Ls1 illustratedin FIG. 23, the pitch (interval) ΔW3 between edges of the adjacent wiresg4 and g5 illustrated in FIG. 25-2 is the same as the pitch ΔW3 betweenthe edges of the adjacent wires g5 and g6. Similarly, in the sensingarea Ls2 illustrated in FIG. 23, the pitch ΔW4 between the edges of theadjacent wires g4 and g5 illustrated in FIG. 25-2 is the same as thepitch ΔW4 between the edges of the adjacent wires g5 and g6. Therefore,the same tangential angle is retained among the wires g4, g5, and g6, ineach of the sensing area Ls1 and the sensing area Ls2.

The wires g4, g5, and g6 are arranged in a manner not intersecting oneanother, and in such a manner that each of the tangential directionschanges continuously. As a result, the wire grid pattern according tothe embodiment is arranged in such a manner that the pitch ΔW3 and thepitch ΔW4 illustrated in FIG. 25-2 are different between the areas wherethe tangential angles are different, for example. For example, the pitchΔW4 in the area where the adjacent wires g4 and g5 are curved (wound) isset wider than the pitch ΔW3 in the area where the wires g4 and g5 arelinear. Such a configuration allows a plurality of wires to be arrangedeasily in a manner allowing each of the tangential directions to changecontinuously. By arranging the wires g4, g5, and g6 at the sameregularity, the signal tracks T11 having the wire grid patternillustrated in FIG. 23 can be achieved on the optical scale 11A.

As the optical scale 11A, the wire grid pattern as illustrated in FIG.23 may be directly formed on the outer circumferential surface of thecylindrical rotor 10A through vapor deposition, for example. The opticalscale 11A may also be produced by forming the wire grid pattern asillustrated in FIG. 23 on an elastic and transparent base member, and bywinding the base member around the outer circumferential surface of thecylindrical rotor 10A.

FIG. 26 is a schematic for explaining a relation between a rotationangle and a polarization axis direction in the optical scale accordingto the second embodiment. In FIG. 26, r denotes the radius of the rotor10A, and zr denotes the rotational center of the rotor 10A. When therotor 10A is rotated, the sensing area Ls1 of the optical sensor package31A moves to the sensing area Ls2. θrot denotes a rotation angle of therotor 10A.

The computing unit 3 illustrated in FIG. 3 acquires the signal intensityI(−) of the component having the first polarization direction and thesignal intensity I(+) of the component having the second polarizationdirection that are the detection signals from the optical sensor 35. Thecomputing unit 3 then calculates the differential signal V from thesignal intensity I(−) of the component having the first polarizationdirection and the signal intensity I(+) of the component having thesecond polarization direction, following Equation (3) below.V=[I(+)−I(−)]/[I(+)+I(−)]=sin(2θs)  (3)

Because the differential signal V calculated from Equation (3) does notinclude parameters affected by the light intensity of the light source41A, the encoder 2 can reduce the influences of fluctuations such asthose in the distance between the optical sensor 35A and the opticalscale 11A, and in the light intensity of the light source 41A.Furthermore, the encoder 2 can detect a change in the polarizationdirection via the differential signal V in a manner less affected byforeign substances.

The relation between the rotation angle and the differential signal inthe optical sensor according to the second embodiment is the same asthat in the optical sensor according to the first embodiment illustratedin FIG. 14.

As mentioned earlier, the vertical axis in FIG. 14 represents thedifferential signal V, and the horizontal axis represents the rotationangle θrot illustrated in FIG. 26. When the rotation angle θrot is 360degrees, that is, when the optical scale 11A is rotated once about therotational center zr, the differential signal V indicates a waveformwith six cycles. This waveform matches the wire pattern illustrated inFIG. 23, having a wave-like form with six cycles in the 360 degrees. Thewaveform of the differential signal V illustrated in FIG. 14 is a sinewave, for example. The number of waves is merely an example, and is notlimited to the number of cycles described above. Although thedifferential signal V has different phases for the transmissive lightand for the reflected light, the differential signal V remains the samein having a waveform with six cycles.

For example, the computing unit 3 can calculate the tangential angle θsfrom the relation between the tangential angle θs and the rotation angleθrot, and the differential signal V expressed by Equation (3) mentionedabove. A change ratio of θs per θrot can be expressed as Equation (4)below, where the maximum angle θmax denotes the rotational angle, whichis related to the number of waves (curves), on the optical scale 11 ofwhen the tangential angle θs is changed by the maximum degree.

$\begin{matrix}{\frac{{\mathbb{d}\theta}\; s}{{\mathbb{d}\theta}\;{rot}} = {\pm \frac{\left( {\pi/4} \right)}{\theta\;\max}}} & (4)\end{matrix}$

Information of the relation between the rotation angle θrot and thedifferential signal V can be acquired by substituting θs calculated fromEquation (4) in Equation (3). The computing unit 3 can then calculatethe rotation angle θrot from the differential signal V from thedetection signal of the optical sensor 35, based on the information ofthe relation between the rotation angle θrot and the differential signalV.

The computing unit 3 stores the information representing the relationbetween the rotation angle θrot and the differential signal Villustrated in FIG. 14 in at least one of the RAM 4 e and the internalstorage device 4 f, so that the CPU 4 c can calculate the number ofrotations of the rotor 10A from the information of the differentialsignal V.

Modification of Encoder

FIG. 27 is a schematic of a structure of an encoder according to amodification of the second embodiment. The members that are the same asthose described above are assigned with the same reference numerals, andredundant explanations thereof are omitted hereunder. This encoder unit1C includes the rotor 10A serving as a shaft connected to a rotarymachine such as a motor, the stator 20A, and an optical sensor package31B capable of reading the signal patterns. The stator 20A is fixedindependently of the rotor 10A. An optical scale 11B has the wire gridpattern as illustrated in FIG. 23, on the outer circumferential surfaceof the cylindrical rotor 10A.

The rotor 10A is rotated with the optical scale 11B. The optical scale11B has the signal tracks T11 that are the wire grid pattern. Theoptical sensor package 31B is fixed to the stator 20A. The opticalsensor package 31B includes an optical sensor 35B capable of reading thesignal tracks T11 on the optical scale 11B.

A light source 41B is supported by a mount member 20B and a mount member20C that are fixed to the stator 20A, and interposed between the rotor10A and the optical scale 11B. The optical sensor 35B is the same as theoptical sensor 35 described above. The light source 41B is the same asthe light source 41 described above. With this structure, the lightsource 41B comes to be arranged at a position facing the optical sensor35B across the optical scale 11B. Therefore, the light source light 71from the light source 41B is passed through the signal tracks T11 on theoptical scale 11B, and the optical sensor 35B can detect thetransmissive light 73 thus passed through as incident light. When therotor 10A is rotated, the signal tracks T11 on the optical scale 11Bmove relatively to the optical sensor package 31B.

The encoder according to the embodiment includes the encoder unit 1C andthe computing unit 3, and the optical sensor 35B in the encoder unit 1Cis connected to the computing unit 3, in the same manner as illustratedin FIG. 3. The computing unit 3 is connected to the control unit 5 ofthe rotary machine such as a motor.

As the signal tracks T11 illustrated in FIG. 23, an arrangement of wiresg, which is referred to as a wire grid pattern, is formed on the opticalscale 11B illustrated in FIG. 27. Provided between the adjacent wires gis a transmissive area w through which the entire or a part of the lightsource light 71 is allowed to pass. When the width of the wire g and thepitch between the adjacent wires g, that is, the width of the wire g andthe width of the transmissive area w, are made sufficiently smaller thanthe wavelength of the light source light 71 from the light source 41,the optical scale 11B can polarize the transmissive light 73 of thelight source light 71.

As mentioned earlier, in the encoder 2, the optical scales 11A, 11B arearranged in a manner not intersecting each other, and in such a mannerthat each of the tangential directions changes continuously. The encoder2 is also provided with an optical sensor including the first polarizinglayer that splits incident light to the light with the firstpolarization direction and on which the light source light from thelight source 41A, 41B passing through or reflected on the optical scale11A, 11B becomes incident, the first photoreceiver for receiving thefirst polarized light split by the first polarizing layer, the secondpolarizing layer that splits the incident light to the light with thesecond polarization direction, and a second photoreceiver for receivingthe second polarized light split by the second polarizing layer. Thecomputing unit 3 serving as a computing unit calculates the amount ofrelative movement between the optical scale 11A, 11B and the opticalsensor 35A, 35B from the intensity of the first polarized light and theintensity of the second polarized light.

Using this structure, the optical sensors 35A, 35B detect a rotationangle of the rotor 10A by splitting the incident light into polarizedcomponents. Therefore, the encoder 2 can reduce the influence offluctuations in the amount of detected light caused by foreignsubstances or the like compared with when the intensity of the incidentlight is directly detected. Because the tolerance of foreign substancesis increased, the encoder can be used in an increased number ofenvironments. Furthermore, the encoder 2 can reduce the influence offluctuations in the amount of detected light due to precisions in theoptical path (the distance from the optical scale to the opticalsensor), even when used is an optical encoder unit. As a result, thearrangement of the light source 41A, 41B and the optical sensor 35A, 35Bcan be designed more freely. In this manner, the encoder unit 2 can bereduced in size, for example. Furthermore, an optical encoder can alsoachieve a higher resolution, compared with a magnetic encoder.

Third Embodiment

FIG. 28 is a schematic of an encoder unit according to a thirdembodiment of the present invention. FIG. 29 is a schematic forexplaining an example of a wire grid pattern on the optical scaleaccording to the third embodiment. FIG. 30 is a schematic for explaininga relation between a rotation angle and a differential signal in theoptical sensor according to the third embodiment. The members that arethe same as those described above are assigned with the same referencenumerals, and redundant explanations thereof are omitted hereunder. Anencoder unit 1D includes an optical scale 11D, and an optical sensorpackage 31D capable of reading signal patterns. The optical scale 11D ismoved in the U direction, for example, so that the relative positionwith respect to the optical sensor package 31D is changed.

The optical scale 11D has the signal tracks T11 that are the wire gridpattern described above. The optical sensor package 31D includes anoptical sensor 35D capable of reading the signal tracks T11 on theoptical scale 11D.

A light source 41D is arranged at a position facing the optical sensor35D across the optical scale 11D. The optical sensor 35D is the same asthe optical sensor 35 described above. The light source 41D is the sameas the light source 41 described above. Therefore, the light sourcelight 71 from the light source 41D is passed through the signal tracksT11 on the optical scale 11D, and the optical sensor 35D can detect thetransmissive light 73 thus passed through as the incident light. Whenthe optical scale 11D is moved linearly in the U direction by a linearmotion mechanism, for example, the signal tracks T11 on the opticalscale 11D move relatively to the optical sensor package 31D.

The encoder according to the embodiment includes the encoder unit 1D andthe computing unit 3, and the optical sensor 35D in the encoder unit 1Dis connected to the computing unit 3, in the same manner as illustratedin FIG. 3. The computing unit 3 is connected to a control unit 5 of alinear motion device or the like.

As the signal tracks T11, an arrangement of wires g, which is referredto as a wire grid pattern, is formed on the optical scale 11Dillustrated in FIG. 29. Provided between the adjacent wires gillustrated in FIG. 29 is a transmissive area w through which the entireor a part of the light source light 71 is allowed to pass. When thewidth of the wire g and the pitch between the adjacent wires g, that is,the width of the wire g and the width of the transmissive area w, aremade sufficiently smaller than the wavelength of the light source light71 from the light source 41D, the optical scale 11D illustrated in FIG.29 can polarize the transmissive light 73 of the light source light 71.

The computing unit 3 illustrated in FIG. 3 acquires the signal intensityI(−) of the component having the first polarization direction and thesignal intensity I(+) of the component having the second polarizationdirection that are detection signals from the optical sensor 35D. Thecomputing unit 3 calculates the differential signal V from the signalintensity I(−) of the component having the first polarization directionand the signal intensity I(+) of the component having the secondpolarization direction, following Equation (3) mentioned above.

The computing unit 3 stores information of a relation between a movementdistance L⁻¹, L₀, l₁, L₂ illustrated in FIG. 29 and the differentialsignal V (see FIG. 30) in at least one of the RAM 4 e and the internalstorage device 4 f, so that the CPU 4 c can calculate the amount ofrelative movement between of the optical scale 11D from the informationof the differential signal V.

Modification of Encoder

FIG. 31 is a schematic of a structure of an encoder according to amodification of the third embodiment. The members that are the same asthose described above are assigned with the same reference numerals, andredundant explanations thereof are omitted hereunder. An encoder unit 1Eincludes the optical scale 11D and an optical sensor package 31D capableof reading signal patterns. The optical scale 11D is moved in the Udirection, for example, so that the relative position with respect tothe optical sensor package 31D is changed.

The optical scale 11D has the signal tracks T11 that are the wire gridpattern. The optical sensor package 31D includes an optical sensor 35Dcapable of reading the signal tracks T11 on the optical scale 11D andthe light source 41D. The light source light 71 from the light source41D is reflected on the signal tracks T11 on the optical scale 11D, andthe optical sensor 35 detects the reflected light 72 thus reflected asincident light.

The encoder according to the embodiment includes the encoder unit 1E andthe computing unit 3, and the optical sensor 35D in the encoder unit 1Eis connected to the computing unit 3, in the same manner as illustratedin FIG. 3. The computing unit 3 is connected to the control unit 5 of alinear motion apparatus or the like.

As the signal tracks T11 illustrated in FIG. 23, an arrangement of wiresg, which is referred to as a wire grid pattern, is formed on the opticalscale 11D illustrated in FIG. 29. Provided between the adjacent wires gis a transmissive area w through which the entire or a part of the lightsource light 71 is allowed to pass. When the width of the wire g and thepitch between the adjacent wires g, that is, the width of the wire g andthe width of the transmissive area w, are made sufficiently smaller thanthe wavelength of the light source light 71 from the light source 41D,the optical scale 11D can polarize the reflected light 72 of the lightsource light 71.

The computing unit 3 illustrated in FIG. 3 acquires the signal intensityI(−) of the component having the first polarization direction and thesignal intensity I(+) of the component having the second polarizationdirection that are the detection signals from the optical sensor 35. Thecomputing unit 3 then calculates the differential signal V from thesignal intensity I(−) of the component having the first polarizationdirection and the signal intensity I(+) of the component having thesecond polarization direction, following Equation (3) mentioned above.

The computing unit 3 stores the information of the relation between themovement distance L⁻¹, L₀, l₁, L₂ illustrated in FIG. 29 and thedifferential signal V (see FIG. 30) in at least one of the RAM 4 e andthe internal storage device 4 f, so that the CPU 4 c can calculate theamount of relative movement of the optical scale 11D from theinformation of the differential signal V. The modifications illustratedin FIGS. 28 and 31 are applicable as a linear encoder.

As mentioned earlier, the encoder 2 includes the optical scale 11Dprovided with a plurality of wires arranged in a manner not intersectingone another, and in a manner so that each of the tangential directionschanges continuously. The encoder 2 also includes the optical sensor35D. The optical sensor 35D is provided with the first polarizing layerthrough or on which the light source light 71 from the light source 41Dis passed or reflected becomes incident on the optical scale 11D, andthat splits the incident light to the light with the first polarizationdirection, and the first photoreceivers receiving the first polarizedlight split by the first polarizing layer. The optical sensor 35D isalso provided with the second polarizing layer that splits the incidentlight to the light with the second polarization direction, and thesecond photoreceivers receiving the second polarized light split by thesecond polarizing layer. The computing unit 3 serving as a computingunit then calculates the amount of relative movement of the opticalscale 11D with respect to the optical sensor 35D from the intensity ofthe first polarized light and the intensity of the second polarizedlight.

With this structure, the optical sensor detects the amount of movementin the U direction using the polarizations of the transmissive light orreflected light thus split. Therefore, the encoder 2 can reduce theinfluence of fluctuations in the amount of detected light caused byforeign substances or the like, compared with when the intensity of theincident light is directly detected. Because the tolerance of foreignsubstances is increased, the encoder can be used in an increased numberof environments. Furthermore, even when used is an optical encoder unit,the encoder 2 can reduce the influence of fluctuations in the amount ofdetected light due to precisions in the optical path (the distance fromthe optical scale to the optical sensor). As a result, the arrangementof the light sources and the optical sensors can be designed morefreely. In this manner, for example, the encoder unit can be reduced insize. Furthermore, an optical encoder can also achieve a higherresolution, compared with a magnetic encoder.

Fourth Embodiment

FIG. 32 is an exploded perspective view for explaining main componentsof a torque sensor according to a fourth embodiment of the presentinvention. FIG. 33-1 is a schematic for explaining an arrangement ofoptical scales and optical sensors in the torque sensor according to thefourth embodiment. FIG. 33-2 is a schematic for schematically explainingthe optical scales and the optical sensors in the torque sensoraccording to the fourth embodiment. This torque sensor 101A will beexplained in detail with reference to FIGS. 32 to 33-2. The members thatare the same as those described above are assigned with the samereference numerals, and redundant explanations thereof are omittedhereunder.

The torque sensor 101A includes a first rotating shaft 110A, a secondrotating shaft 110B, a torsion bar 129, an optical scale 11AT, anoptical sensor 35AT, a light source 41AT, an optical scale 11BT, anoptical sensor 35BT, and a light source 41BT provided inside of thehousing 120. The torque sensor 101A is referred to as an axial torquesensor.

Mounted on one end of the torsion bar 129 is the first rotating shaft110A, and mounted on the other end of the torsion bar 129 (the end onthe opposite side of the end on which the first rotating shaft 110A ismounted) is the second rotating shaft 110B. In other words, one end ofthe torsion bar 129 is provided with the first rotating shaft 110A, andthe other end is provided with the second rotating shaft 110B. The firstrotating shaft 110A is connected to an input shaft, for example, and thesecond rotating shaft 110B is connected to an output shaft. The firstrotating shaft 110A and the second rotating shaft 110B are supportedrotatably by the housing 120 via a bearing 126A and a bearing 126B,respectively.

In the torque sensor 101A, the first rotating shaft 110A may bemanufactured integrally with the input shaft, and the second rotatingshaft 110B may be manufactured integrally with the output shaft. Thisstructure allows the input shaft, the first rotating shaft 110A, thetorsion bar 129, the second rotating shaft 110B, and the output shaft tobe positioned coaxially. In the embodiment, the first rotating shaft110A is connected to the one end of the torsion bar 129 unrotatably, andthe other end of the torsion bar 129 is connected to the second rotatingshaft 110B unrotatably. When a torque is applied to the torsion bar 129,torsion is generated in the torsion bar 129. In other words, when atorque is applied via the first rotating shaft 110A, the first rotatingshaft 110A is rotationally displaced with respect to the second rotatingshaft 110B, whereby causing torsion to be produced in the torsion bar129.

The first rotating shaft 110A is an approximately cylindrical member. Inthe embodiment, the optical scale 11AT is provided on the outercircumference of the first rotating shaft 110A. In the embodiment, theoptical scale 11AT protrudes outwardly from the outer circumference ofthe first rotating shaft 110A, and has a ring-like shape along thecircumferential direction of the first rotating shaft 110A.

The second rotating shaft 110B is an approximately cylindrical member.The optical scale 11BT is provided on the outer circumference of thesecond rotating shaft 110B. In the embodiment, the optical scale 11BTprotrudes outwardly from the outer circumference of the second rotatingshaft 110B, and has a ring-like shape along the circumferentialdirection of the second rotating shaft 110B.

As illustrated in FIGS. 32 to 33-2, at least two pairs of light sources41AT, 41BT and optical sensor packages 31AT, 31BT are arranged andprovided outside of the first rotating shaft 110A and the secondrotating shaft 110B, respectively, along the direction of the rotationalaxis Zr of the first rotating shaft 110A and the second rotating shaft110B. In the embodiment, two pairs of the light source and the opticalsensor are provided, but the number of the light sources and the opticalsensors is not limited thereto. These pairs of the light source 41AT andthe optical sensor package 31AT, and the light source 41BT and theoptical sensor package 31BT are combinations of the same light sourceand optical sensor, and are positioned inside of the housing 120.

The torque sensor 101A detects a relative displacement (rotationaldisplacement) between the first rotating shaft 110A and the secondrotating shaft 110B that are connected via the torsion bar 129, byreflecting a detection result from the optical sensor package 31AT whichreads the optical scale 11AT or a detection result from the opticalsensor package 31BT which reads the optical scale 11BT.

The optical scales 11AT, 11BT are made of silicon, glass, or a polymermaterial, for example. The optical scales 11AT, 11BT both have thesignal tracks T1 on one or both of the surfaces. As illustrated in FIGS.33-1 and 33-2, the light source 41AT is arranged at a position facingthe optical sensor 35AT across the optical scale 11AT. The light source41BT is arranged at a position facing the optical sensor 35BT across theoptical scale 11BT.

FIG. 34 is a schematic for explaining an arrangement of the opticalscales and the optical sensors in the torque sensor according to thefourth embodiment. In the same manner as in the optical sensor 35illustrated in FIG. 2-2, the optical sensor 35AT illustrated in FIG. 34is capable of reading signal tracks T1 on the optical scale 11AT, andthe light source 41AT is arranged at a position facing the opticalsensor 35AT across the optical scale 11AT. With this structure, a lightsource light 71AT from the light source 41AT is passed through thesignal tracks T1 on the optical scale 11AT, and the optical sensor 35ATdetects a transmissive light 73AT thus passed through as incident light.A relation between the optical sensor 35BT, the optical scale 11BT, andthe light source 41BT is the same as the relation between the opticalsensor 35AT, the optical scale 11AT, and the light source 41AT. Withthis structure, a light source light 71BT from the light source 41BT ispassed through the signal tracks T1 on the optical scale 11BT, and theoptical sensor 35BT detects a transmissive light 73BT thus passedthrough as incident light.

As the first rotating shaft 110A is rotated, the signal tracks T1 on theoptical scale 11AT move relatively to the optical sensor 35AT. As thesecond rotating shaft 110B is rotated, the signal tracks T1 on theoptical scale 11BT moves relatively to the optical sensor 35BT.

FIG. 35 is a block diagram of a torque detection apparatus according tothe fourth embodiment. This torque detection apparatus 200 includes thetorque sensor 101A and the computing unit 3. The optical sensor 35AT andthe optical sensor 35BT in the torque sensor 101A are connected to thecomputing unit 3, as illustrated in FIG. 35. The computing unit 3 isconnected to the control unit 5 of the rotary machine such as a motor.

The torque detection apparatus 200 uses the optical sensors 35AT and35BT to detect the incident transmissive light 73AT and 73BT that is thelight source light 71AT and 71BT having passed through the respectiveoptical scales 11AT and 11BT. The computing unit 3 calculates a relativeposition of the first rotating shaft 110A with respect to the opticalsensor package 31AT in the torque sensor 101A from the detection signalfrom the optical sensor 35AT. The computing unit 3 also calculates arelative position of the second rotating shaft 110B with respect to theoptical sensor package 31BT in the torque sensor 101A from the detectionsignal from the optical sensor 35BT.

The computing unit 3 stores the torsional elastic coefficient of thetorsion bar 129 in the RAM 4 e and the internal storage device 4 f.Torque is proportional to a torsional elastic coefficient of the torsionbar 129. Therefore, in order to acquire torsion, the computing unit 3calculates the rotational displacement (the amount of displacement) ofthe rotation angle of the first rotating shaft 110A with respect to therotation angle of the second rotating shaft 110B. The computing unit 3can then calculate the torque from the elastic coefficient of thetorsion bar 129 and the information of the relative positions of thefirst rotating shaft 110A and the second rotating shaft 110B. Thecomputing unit 3 then outputs the torque to the control unit 5 of arotary machine (motor) or the like, as a control signal.

The computing unit 3 is a computer such as a PC, and includes the inputinterface 4 a, the output interface 4 b, the CPU 4 c, the ROM 4 d, theRAM 4 e, and the internal storage device 4 f. The input interface 4 a,the output interface 4 b, the CPU 4 c, the ROM 4 d, the RAM 4 e, and theinternal storage device 4 f are connected via an internal bus. Thecomputing unit 3 may be configured as a dedicated processing circuit.

The input interface 4 a receives input signals from the optical sensors35AT and 35BT in the torque sensor 101A, and outputs the signals to theCPU 4 c. The output interface 4 b receives the control signal from theCPU 4 c, and outputs the control signal to the control unit 5.

The ROM 4 d stores therein computer programs such as a BIOS. Theinternal storage device 4 f is a HDD or a flash memory, for example, andstores therein an operating system program and application programs. TheCPU 4 c implements various functions by executing the computer programsstored in the ROM 4 d or in the internal storage device 4 f, using theRAM 4 e as a working area.

The internal storage device 4 f stores therein a database in which apolarization axis of each of the optical scales 11AT, 11BT, which aredescribed later, is associated with an output of the correspondingoptical sensor 35AT, 35BT.

As the signal tracks T1, an arrangement of wires g, which is referred toas a wire grid pattern, illustrated in FIG. 4 is formed on each of theoptical scales 11AT and 11BT illustrated in FIGS. 32 to 33-2.

The wires g are arranged in a manner not intersecting one another, andin such a manner that each of the tangential directions changescontinuously. Provided between the adjacent wires g is a transmissivearea w through which the entire or a part of the light source light71AT, 71BT is allowed to pass. When the width of the wire g and thepitch between the adjacent wires g, that is, the width of the wire g andthe width of the transmissive area w, are made sufficiently smaller thanthe wavelength of the light source light 71AT, 71BT, the optical scale11AT, 11BT can polarize the transmissive light 73AT, 73BT of the lightsource light 71AT, 71BT.

This structure allows the polarization of the transmissive light 73AT,73BT (or reflected light) to change correspondingly to the tangentialdirection, which is dependent on the position where the light sourcelight 71AT, 71BT output to the optical scale 11AT, 11BT is passedthrough. Therefore, each of the optical scales 11AT, 11BT does not needto be provided with highly granular segments each having a differentpolarizing direction. As a result, the optical scales 11AT, 11BT allow ahigh resolution to be achieved even when the size of the optical scaleis reduced. When the sizes of the optical scales 11AT, 11BT are reduced,the arrangement of the light sources 41AT, 41BT and the optical sensors35AT, 35BT can be designed more freely. Furthermore, the optical scale11AT, 11BT can have a higher heat resistance, compared with aphoto-induced polarizer. Moreover, because the optical scale 11AT, 11BThas a line pattern without any intersections even locally, a highlyaccurate optical scale with a smaller error can be achieved.Furthermore, because the optical scales 11AT, 11BT can be manufacturedstably with a bulk-exposure, a highly accurate optical scale with asmaller error can be achieved.

As the tangential angle of the wire grid pattern changes, thepolarization axis of the incident light that becomes incident on theoptical sensor 35AT changes correspondingly to the rotation of theoptical scale 11AT. Therefore, by detecting a change in the polarizationaxis, the rotation of the optical scale 11AT can be recognized.Explained now is the optical sensor 35AT according to the fourthembodiment that detects a change in the polarization axis and serves asa polarization splitting unit. Because the optical sensor 35BT is thesame as the optical sensor 35AT, a detailed explanation of the opticalsensor 35BT is omitted herein.

In the same manner as in the optical sensor 35 illustrated in FIG. 15-1,the optical sensor 35AT includes a first optical sensor 36A and a secondoptical sensor 36B. The first optical sensor 36A includes a sensor base36Ka and the first photoreceivers 36 a, and is capable of detecting theintensity of light with the first polarization direction. Each of thefirst photoreceivers 36 a is provided with the first polarizing layerthat splits incident light to the light with the first polarizationdirection, and receives the first polarized light split by the firstpolarizing layer.

The second optical sensor 36B includes the sensor base 36Kb and thesecond photoreceivers 36 b, and is capable of detecting the intensity oflight with the second polarization direction. Each of the secondphotoreceivers 36 b is provided with the second polarizing layer thatsplits the incident light to the light with the second polarizationdirection, and receives the second polarized light split by the secondpolarizing layer. Each of the first photoreceivers 36 a and the secondphotoreceivers 36 b is configured in a comb-like shape, as illustratedin FIG. 15-1, engaging and spaced uniformly with each other.

This structure allows the incident light to be split into the firstpolarized light and the second polarized light. As a result, thecomputing unit can calculate the polarization angle of the transmissivelight or the reflected light based on the signal intensities of thepolarized component having the first polarization direction and of thepolarized component having the second polarization direction thus split.The first polarization direction and the second polarization directionare preferably different from each other by 90 degrees to allow thecomputing unit to calculate the polarization angle easily.

The computing unit 3 acquires the signal intensity I(−) of the componenthaving the first polarization direction and the signal intensity I(+) ofthe component having the second polarization direction that aredetection signals from the optical sensor 35AT. The computing unit 3then calculates the differential signal V following Equation (1) below,from the signal intensity I(−) of the component having the firstpolarization direction and the signal intensity I(+) of the componenthaving the second polarization direction

Because the differential signal V calculated from Equation (1) does notinclude parameters affected by the light intensity of the light sourcelight 71AT, the torque detection apparatus 200 can reduce the influencesof fluctuations such as those in the distance between the optical sensor35AT and the optical scale 11AT, and in the light intensity of the lightsource 41AT. Therefore, even when the intensity of the incident light isdecreased by a foreign substance, the torque detection apparatus 200 candetect a change in the polarization direction Pm via the differentialsignal V, in a manner less affected by foreign substances.

In FIG. 14, the vertical axis represents the differential signal V andthe horizontal axis represents the rotation angle θrot illustrated inFIG. 6. When the rotation angle θrot is 360 degrees, that is, when theoptical scale 11AT is rotated once, the differential signal V indicatesa waveform with six cycles. This waveform matches the cycles of thecurves in the wire pattern illustrated in FIG. 4 having a wave-like formwith six cycles in the 360 degrees. The waveform of the differentialsignal V illustrated in FIG. 14 is a sine wave, for example. The numberof waves is merely an example, and is not limited to the number ofcycles described above. Although the differential signal V has differentphases for the transmissive light and for the reflected light, thedifferential signal V remains the same in having a waveform with sixcycles.

The computing unit 3 stores information representing the relationbetween the rotation angle θrot and the differential signal Villustrated in FIG. 14 in at least one of the RAM 4 e and the internalstorage device 4 f, so that the CPU 4 c can calculate the number ofrotations or the rotation angles of the first rotating shaft 110A and ofthe second rotating shaft 110B from the information of the differentialsignal V. In other words, the torque detection apparatus 200 also has afunction of an angle sensor. Therefore, a separate angle sensor does notneed to be provided, so that torque detection apparatus 200 can reducecosts.

The computing unit 3 can calculate the amount of torque from the amountof difference between the rotation angle of the first rotating shaft110A and the rotation angle of the second rotating shaft 110B, and fromthe elastic coefficient of the torsion bar 129.

The computing unit 3 also calculates the rotation angle θrot from thedifferential signal V. The computing unit 3 can then calculate thetangential angle θd from the relation between the tangential angle θdand the rotation angle θrot illustrated in FIG. 7 and the differentialsignal V indicated in Equation (1) above. By providing the optical scale11AT with the wire grid pattern in which the tangential angle θd and themaximum angle θmax illustrated in FIG. 7 are changed by given degrees,the torque detection apparatus 200 can achieve a detection apparatushaving the relation between the rotation angle and the differentialsignal. Because the relation between the optical scale 11BT and theoptical sensor 35BT is the same as that between the optical scale 11ATand the optical sensor 35AT described above, a detailed explanationthereof is omitted herein.

As described earlier, the torque detection apparatus 200 detects torqueusing torsion of a torsion bar 129. The first rotating shaft 110A andthe second rotating shaft 110B are connected via the torsion bar 129 inwhich torsion is generated when a torque is applied. The torquedetection apparatus 200 includes the optical scale 11AT moving with therotation of the first rotating shaft 110A, the optical scale 11BT movingwith the rotation of the second rotating shaft 110B, the optical sensor35AT paired with the optical scale 11AT, and the optical sensor 35BTpaired with the optical scale 11BT. The torque detection apparatus 200detects the polarization of the transmissive light that changesdepending on the position where the light source light output to theoptical scale 11AT and the optical scale 11BT is passed through. In thetorque detection apparatus 200, the computing unit 3 serving as acomputing unit calculates a relative rotation angle of the optical scale11AT with respect to the optical sensor 35AT, calculates a relativerotation angle of the optical scale 11BT with respect to the opticalsensor 35BT, and calculates rotational displacements of the firstrotating shaft 110A and the second rotating shaft 110B.

With this structure, these optical sensors detect rotational angles of aplurality of respective optical scales that are caused to rotate as therespective first and second rotating shafts are rotated, using thepolarizations of the transmissive light or the reflected light thussplit. Therefore, compared with when the light intensity of thetransmissive light is directly detected, the torque detection apparatuscan reduce the influence of fluctuations in the amount of detected lightcaused by foreign substances or the like, even when used are opticaltorque sensors. Because the tolerance of foreign substances isincreased, the torque detection apparatus can be used in an increasednumber of environments. Furthermore, the torque detection apparatus canreduce the influence of fluctuations in the amount of detected light dueto precisions in the optical path (the distance from the optical scaleto the optical sensor), even when used are optical torque sensors. As aresult, the arrangement of the light sources and the optical sensors canbe designed more freely. In this manner, the torque sensors in thetorque detection apparatus can be reduced in size. The torque detectionapparatus can also achieve a higher resolution, compared with a magnetictorque sensor.

Modification of Torque Sensor

FIG. 36 is a schematic for explaining an exemplary modification of thetorque sensor according to the fourth embodiment. The members that arethe same as those described above are assigned with the same referencenumerals, and redundant explanations thereof are omitted hereunder. Thistorque sensor 101B includes a first rotating shaft 110C, a secondrotating shaft 110D, the torsion bar 129, the optical scale 11AT, theoptical sensor 35AT, the light source 41AT, the optical scale 11BT, theoptical sensor 35BT, and the light source 41BT provided inside of thehousing 120 illustrated in FIG. 32. The torque sensor 101B is referredto as an embedded torque sensor.

Mounted on one end of the torsion bar 129 is the first rotating shaft110C, and mounted on the other end (the end on the opposite side of theend on which the first rotating shaft 110C is mounted) is the secondrotating shaft 110D. In other words, one end of the torsion bar 129 isprovided with the first rotating shaft 110C, and the other end isprovided with the second rotating shaft 110D. The first rotating shaft110C is embedded in the second rotating shaft 110D, and is supportedrotatably via a bearing. This structure allows the torque sensor 101B tobe reduced in length in the axial direction of the rotational axis Zr.

Fifth Embodiment

FIG. 37 is a schematic for explaining a torque sensor according to afifth embodiment of the present invention. The members that are the sameas those described above are assigned with the same reference numerals,and redundant explanations thereof are omitted hereunder. This torquesensor 101C includes the first rotating shaft 110A, the second rotatingshaft 110B, the torsion bar 129, an optical scale 11CT, an opticalsensor 35AT, the light source 41AT, an optical scale 11DT, the opticalsensor 35BT, and the light source 41BT provided inside of the housing120 illustrated in FIG. 32.

In the torque sensor 101C, the direction from the light source 41ATtoward the optical sensor 35AT is orientated the same as the directionfrom the light source 41BT toward the optical sensor 35BT. The lightsource 41AT, the optical sensor 35AT, the light source 41BT, and theoptical sensor 35BT are positioned so that optical path from the lightsource 41AT to the optical sensor 35AT and the optical path from thelight source 41BT to the optical sensor 35BT are offset from each otherin the radial direction.

Both of the optical scale 11CT and the optical scale 11DT have thesignal tracks T1, in the same manner as the optical scale 11AT and theoptical scale 11BT described above. The signal tracks T1 on the opticalscale 11CT are positioned on the optical path from the light source 41ATto the optical sensor 35AT, and the signal tracks T1 on the opticalscale 11DT are positioned on the optical path from the light source 41BTto the optical sensor 35BT. Therefore, the optical scale 11CT has alarger diameter than that of the optical scale 11DT, for example.

In the torque sensor 101C according to the fifth embodiment, the opticalscale 11CT has a larger diameter than the optical scale 11DT. The lighthaving passed through the optical scale 11CT is passed through theoptical scale 11DT, and reaches the optical sensor package 31BT. In thismanner, because the tolerance of foreign substances is increased, thetorque sensor 101C can be used in an increased number of environments.Furthermore, because the influence of fluctuations in the amount ofdetected light can be reduced, the optical sensor 35BT can detect eventhe transmissive light having passed through the optical scale 11CT andthe optical scale 11DT. As a result, with the torque sensor 101Caccording to the fifth embodiment, the arrangement of the light sourcesand the optical sensors can be designed more freely.

Sixth Embodiment

FIG. 38 is a schematic for explaining a torque sensor according to asixth embodiment of the present invention. The members that are the sameas those described above are assigned with the same reference numerals,and redundant explanations thereof are omitted hereunder. This torquesensor 101D includes the first rotating shaft 110A, the second rotatingshaft 110B, the torsion bar 129, the optical scale 11AT, the opticalsensor 35AT, the light source 41AT, a waveguide 45A, the optical scale11BT, the optical sensor 35BT, the light source 41BT, and a waveguide45B provided inside of the housing 120 illustrated in FIG. 32.

In the torque sensor 101D, the light source 41AT and the optical sensor35AT are arranged adjacent to each other. The light source light fromthe light source 41AT is passed through the optical scale 11AT toachieve transmissive light, and the optical sensor 35AT detects thetransmissive light refracted on the waveguide 45A such as a prism.Similarly, the light source 41BT and the optical sensor 35BT arearranged adjacent to each other in the torque sensor 101D. The lightsource light from the light source 41BT is then passed through theoptical scale 11BT to achieve transmissive light, and the optical sensor35BT detects the transmissive light refracted on the waveguide 45B suchas a prism.

In the torque sensor 101D according to the sixth embodiment, the lightis passed through the waveguides 45A and 45B and reaches the opticalsensors 35AT and 35BT, respectively. In this manner, because thetolerance of foreign substances is increased, the torque sensor 101D canbe used in an increased number of environments. Furthermore, because theinfluence of fluctuations in the amount of detected light can bereduced, the optical sensors 35AT, 35BT can detect the transmissivelight passed through the waveguide 45A, 45B. As a result, with thetorque sensor 101D according to the sixth embodiment, the arrangement ofthe light sources and the optical sensors can be designed more freely.

Seventh Embodiment

FIG. 39 is a schematic for schematically explaining the torque sensoraccording to the seventh embodiment. FIG. 40 is a schematic forexplaining an arrangement of an optical scale and an optical sensor inthe torque sensor according to the seventh embodiment. The members thatare the same as those described above are assigned with the samereference numerals, and redundant explanations thereof are omittedhereunder. This torque sensor 101E includes the first rotating shaft110A, the second rotating shaft 110B, the torsion bar 129, the opticalscale 11AT, the optical sensor package 31AT, the light source 41AT, theoptical scale 11BT, the optical sensor package 31BT, and the lightsource 41BT provided inside of the housing 120 illustrated in FIG. 32.

As illustrated in FIG. 40, the optical sensor packages 31AT, 31BTinclude optical sensors 35AT, 35BT capable of reading the signal tracksT1 on the optical scales 11AT, 11BT, and the light sources 41AT, 41BT,respectively. For example, the light source light 71AT from the lightsource 41AT is reflected on the signal tracks T1, and the optical sensor35AT detects a reflected light 72AT thus reflected as incident light.

As described earlier, the torque detection apparatus 200 includes theoptical scales 11AT and the optical scale 11BT respectively moving asthe first rotating shaft 110A and the second rotating shaft 110B arerotated, and the optical sensor 35AT and the optical sensor 35BT thatare paired with the optical scale 11AT and the optical scale 11BT,respectively, to detect the polarization of reflected light changingcorrespondingly to the position where the light source light output tothe optical scale 11AT and the optical scale 11BT is reflected. In thetorque detection apparatus 200, the computing unit 3 serving as acomputing unit calculates a relative rotation angle of the optical scale11AT with respect to the optical sensor 35AT, calculates a relativerotation angle of the optical scale 11BT with respect to the opticalsensor 35BT, and calculates rotational displacements of the firstrotating shaft 110A and the second rotating shaft 110B.

With this structure, the optical sensors detect the rotational angles ofa plurality of respective optical scales that are caused to rotate asthe respective first and second rotating shafts are rotated, as thepolarizations of the light split from the reflected light. Therefore,the torque detection apparatus can reduce the influence of fluctuationsin the amount of detected light caused by foreign substances or thelike, compared with when the light intensity of reflected light isdirectly detected, even when used are optical torque sensors. Becausethe tolerance of foreign substances is increased, the torque detectionapparatus can be used in an increased number of environments.Furthermore, the torque detection apparatus can reduce the influence offluctuations in the amount of detected light due to precisions in theoptical path (the distance from the optical scale to the opticalsensor), even when used are optical torque sensors. As a result, thearrangement of the light sources and the optical sensors can be designedmore freely. In this manner, the torque sensors in the torque detectionapparatus can be reduced in size. Furthermore, the torque detectionapparatus can also achieve a higher resolution, compared with a magnetictorque sensor.

Modification of Torque Sensor

FIG. 41 is a schematic for explaining an exemplary modification of thetorque sensor according to the seventh embodiment. The members that arethe same as those described above are assigned with the same referencenumerals, and redundant explanations thereof are omitted hereunder. Thistorque sensor 101F includes the first rotating shaft 110C, the secondrotating shaft 110D, the torsion bar 129, the optical scale 11AT, theoptical sensor package 31AT, the light source 41AT, the optical scale11BT, the optical sensor package 31BT, and the light source 41BT thatare provided inside of the housing 120. The torque sensor 101F isreferred to as an embedded torque sensor.

Mounted on one end of the torsion bar 129 is the first rotating shaft110C, and mounted on the other end (the end on the opposite side of theend to which the first rotating shaft 110C is attached) is the secondrotating shaft 110D. In other words, the one end of the torsion bar 129is provided with the first rotating shaft 110C, and the other end isprovided with the second rotating shaft 110D. The first rotating shaft110C is embedded in the second rotating shaft 110D, and is supportedrotatably via a bearing. With this structure, the torque sensor 101F canreduce the length in the axial direction Zr.

Eighth Embodiment

FIG. 42 is a schematic of a structure of a torque sensor according to aneighth embodiment of the present invention. FIG. 43 is a side view of astructure of the torque sensor according to the eighth embodiment. Themembers that are the same as those described above are assigned with thesame reference numerals, and redundant explanations thereof are omittedhereunder.

This torque sensor 101G includes the first rotating shaft 110A, thesecond rotating shaft 110B, the torsion bar 129, an optical scale 11ET,the optical sensor 35AT, the light source 41AT, an optical scale 11FT,the optical sensor 35BT, and the light source 41BT that are providedinside of the housing 120. The torque sensor 101G is referred to as aradial torque sensor.

Each of the first rotating shaft 110A and the second rotating shaft 110Bis both a cylindrical member. The first rotating shaft 110A and thesecond rotating shaft 110B have the optical scale 11ET and the opticalscale 11FT, respectively, on their outer circumferential surface of thecylindrical members. Each of the optical scale 11ET and the opticalscale 11FT has signal tracks T11 that are the wire grid pattern. Theoptical sensor 35AT and the optical sensor 35BT are both fixed to thehousing 120. When the first rotating shaft 110A is rotated, the signaltracks T11 on the optical scale 11ET moves relatively to the opticalsensor package 31AT. When the second rotating shaft 110B is rotated, thesignal tracks T11 on the optical scale 11FT moves relatively to theoptical sensor package 31BT.

The optical sensor package 31AT includes the optical sensor 35AT capableof reading the signal tracks T11 on the optical scale 11ET, and thelight source 41AT. The light source light 71AT from the light source41AT is reflected on the signal tracks T11 on the optical scale 11ET,and the optical sensor 35AT detects the reflected light 72AT thusreflected as incident light. The optical sensor package 31BT includesthe optical sensor 35BT capable of reading the signal tracks T11 on theoptical scale 11FT, and the light source 41BT. The light source light71BT from the light source 41BT is reflected on the signal tracks T11 onthe optical scale 11FT, and the optical sensor 35BT detects a reflectedlight 72BT thus reflected as incident light. The torque detectionapparatus according to the embodiment is provided with the torque sensor101G and the computing unit 3 described above, and the optical sensor35AT and the optical sensor 35BT in the torque sensor 101G are connectedto the computing unit 3, as illustrated in FIG. 35. The computing unit 3is connected to the control unit 5 of the rotary machine such as amotor.

The signal tracks T11 illustrated in FIG. 23 is an arrangement of wiresg, which is referred to as a wire grid pattern, formed on the opticalscale 11ET and the optical scale 11FT illustrated in FIGS. 42 and 43.

The wire g is arranged in plurality, in such a manner that each of thewires does not intersect with one another, and in such a manner thateach of the tangential directions changes continuously. Provided betweenthe adjacent wires g is a transmissive area w through which the entireor a part of the light source light 71AT, 71BT is allowed to pass. Whenthe width of the wire g and the pitch between the adjacent wires g, thatis, the width of the wire g and the width of the transmissive area w,are made sufficiently smaller than the wavelength of the light sourcelight 71AT, 71BT from the light sources 41AT, 41BT, the optical scale11ET can polarize the reflected light 72AT from the light source light71AT, and the optical scale 11FT can polarize the reflected light 72BTfrom the light source light 71BT.

With this structure, the polarization of the transmissive light or thereflected light can be changed correspondingly to the tangentialdirection, which is dependent on the positions where the light sourcelight output to the optical scales is passed through or is reflected.Therefore, the optical scales do not need to be provided with highlygranular segments each having a different polarizing direction. As aresult, the optical scales allow a high resolution to be achieved evenwhen the sizes of the optical scales is reduced. Furthermore, byreducing the sizes of the optical scales, the arrangement of the lightsources and the optical sensors can be designed more freely.Furthermore, compared with photo-induced polarizers, optical scales havea higher heat resistance. Because the optical scales 11AT, 11BT haveline patterns without any intersections even locally, highly accurateoptical scales with smaller errors can be achieved. Furthermore, becausethe optical scales can be manufactured stably with a bulk-exposure,highly accurate optical scales with smaller errors can be achieved.

The optical scale 11ET and the optical scale 11FT may be achieved bydirectly forming the wire grid patterns illustrated in FIG. 23 on theouter circumferential surface of the cylindrical first rotating shaft110A and second rotating shaft 110B via vapor deposition, for example.The optical scale 11ET and the optical scale 11FT may also be achievedby forming the wire grid patterns illustrated in FIG. 23 on elastic,transparent base members, and winding such base members around therespective outer circumferential surfaces of the cylindrical firstrotating shaft 110A and second rotating shaft 110B.

In the same manner as in FIG. 26, r denotes the radius of the firstrotating shaft 110A and the second rotating shaft 110B, and zr denotesthe rotational center of the first rotating shaft 110A and the secondrotating shaft 110B. When the first rotating shaft 110A and the secondrotating shaft 110B are rotated, the sensing area Ls1 of the opticalsensor 35AT and the optical sensor 35BT moves to the sensing area Ls2.θrot denotes a rotation angle of the first rotating shaft 110A or thesecond rotating shaft 110B.

The computing unit 3 illustrated in FIG. 35 acquires the signalintensity I(−) of the component having the first polarization directionand the signal intensity I(+) of the component having the secondpolarization direction that are detection signals from each of theoptical sensor 35AT and the optical sensor 35BT. The computing unit 3then calculates the differential signal V the signal intensity I(−) ofthe component having the first polarization direction and the signalintensity I(+) of the component having the second polarization directionfollowing Equation (1) mentioned above. Although the differential signalV has different phases for the transmissive light and for the reflectedlight, the differential signal V remains the same in having a waveformwith six cycles.

In FIG. 14, the vertical axis represents the differential signal V andthe horizontal axis represents the rotation angle θrot illustrated inFIG. 26. When the rotation angle θrot is 360 degrees, that is, when theoptical scale 11ET or the optical scale 11FT is rotated once about therotational center zr, the differential signal V indicates a waveformwith six cycles. This waveform matches the cycles of the curves in thewire pattern illustrated in FIG. 23, which has a wave-like form with sixcycles in the 360 degrees. The waveform of the differential signal Villustrated in FIG. 14 is a sine wave, for example. The number of wavesis merely an example, and is not limited to the number of cyclesdescribed above.

The computing unit 3 stores the information representing the relationbetween the rotation angle θrot and the differential signal Villustrated FIG. 26 in at least one of the RAM 4 e and the internalstorage device 4 f, so that the CPU 4 c can calculate the number ofrotations of the first rotating shaft 110A or the second rotating shaft110B from the information of the differential signal V. In other words,the torque detection apparatus 200 also has a function of an anglesensor. Therefore, a separate angle sensor does not need to be provided,so that the torque detection apparatus 200 can reduce costs. Thecomputing unit 3 can calculate the amount of torque from the amount ofdisplacement between the rotation angle of the first rotating shaft 110Aand the rotation angle of the second rotating shaft 110B, and theelastic coefficient of the torsion bar 129.

As described earlier, the torque detection apparatus 200 includes theoptical scale 11ET and the optical scale 11FT that are caused to move asthe first rotating shaft 110A and the second rotating shaft 110B arerotated, respectively, and the optical sensors 35AT and 35BT that arepaired with the optical scale 11ET and the optical scale 11FT,respectively, and that detects the polarization of the reflected lightchanging correspondingly to the positions where the light source lightoutput to the optical scale 11ET and the optical scale 11FT isreflected. In the torque detection apparatus 200, the computing unit 3serving as a computing unit calculates a relative rotation angle of theoptical scale 11ET with respect to the optical sensor 35AT, andcalculates a relative rotation angle of the optical scale 11FT withrespect to the optical sensor 35BT, and calculates rotationaldisplacements of the first rotating shaft 110A and the second rotatingshaft 110B.

With this structure, the optical sensors detect the rotational angles ofa plurality of respective optical scales that are caused to move whenthe respective first and second rotating shafts are rotated, using thepolarizations of the light split from the reflected light. Therefore,the torque detection apparatus can reduce the influence of fluctuationsin the amount of detected light caused by foreign substances or thelike, compared with when the light intensity of reflected light isdirectly detected, even when used are optical torque sensors. Becausethe tolerance of foreign substances is increased, the torque detectionapparatus can be used in an increased number of environments.Furthermore, the torque detection apparatus can reduce the influence offluctuations in the amount of detected light due to precisions in theoptical path (the distance from the optical scale to the opticalsensor), even when used are optical torque sensors. As a result, thearrangement of the light sources and the optical sensors can be designedmore freely. In this manner, the torque sensors in the torque detectionapparatus can be reduced in size. Furthermore, such a torque detectionapparatus can also achieve a higher resolution, compared with a magnetictorque sensor.

Modification of Torque Sensor

FIG. 44 is a schematic of a structure of a torque sensor according to amodification of the eighth embodiment. The members that are the same asthose described above are assigned with the same reference numerals, andredundant explanations thereof are omitted hereunder. This torque sensor101H includes the first rotating shaft 110A, the second rotating shaft110B, the torsion bar 129, an optical scale 11GT, the optical sensor35AT, the light source 41AT, an optical scale 11HT, the optical sensor35BT, and the light source 41BT that are provided inside of the housing120.

Each of the first rotating shaft 110A and the second rotating shaft 110Bis a cylindrical member. The signal tracks T11 illustrated in FIG. 23are an arrangement of wires g, which is referred to as a wire gridpattern, formed on each of the optical scale 11GT and the optical scaleHT. Provided between the adjacent wires g is a transmissive area wthrough which the entire or a part of the light source light 71AT, 71BTis allowed to pass. When the width of the wire g and the pitch betweenthe adjacent wires g, that is, the width of the wire g and the width ofthe transmissive area w, are made sufficiently smaller than thewavelength of the light source light 71AT, 71BT from the light source41AT, 41BT, the optical scale 11GT and the optical scale 11HT canpolarize the transmissive light 73AT from the light source light 71ATand the transmissive light 73BT from the light source light 71BT.

The light source 41AT is supported by a mount member 120B and a mountmember 120C that are fixed to the housing 120, and positioned betweenthe first rotating shaft 110A and the optical scale 11GT. In thisstructure, the light source 41AT is arranged at a position facing theoptical sensor 35AT across the optical scale 11GT. Therefore, the lightsource light 71AT from the light source 41AT is passed through thesignal tracks T11 on the optical scale 11GT, so that the optical sensor35AT can detect the transmissive light 73AT thus passed through asincident light. When the first rotating shaft 110A is rotated, thesignal tracks T11 on the optical scale 11GT move relatively to theoptical sensor 35AT.

The light source 41BT is supported by the mount member 120B and themount member 120C that are fixed to the housing 120, and positionedbetween the second rotating shaft 110B and the optical scale 11HT. Inthis structure, the light source 41BT is arranged at a position facingthe optical sensor 35BT across the optical scale 11HT. Therefore, thelight source light 71BT from the light source 41BT is passed through thesignal tracks T11 on the optical scale 11HT, so that optical sensor 35BTcan detect the transmissive light 73BT thus passed through. When thesecond rotating shaft 110B is rotated, the signal tracks T11 on theoptical scale 11HT move relatively to the optical sensor 35BT.

As described earlier, the torque detection apparatus 200 includes theoptical scales 11GT and 11HT that are caused to rotate as the respectivefirst and second rotating shafts 110A and 110B are rotated, the opticalsensors 35AT and 35BT that are paired with the respective optical scales11GT and 11HT, and that detect the polarization of the transmissivelight that changes correspondingly to the positions where the lightsource light output to the optical scale 11GT and the optical scale 11HTis passed through. In the torque detection apparatus 200, the computingunit 3 serving as a computing unit calculates a relative rotation angleof the optical scale 11GT with respect to the optical sensor 35AT,calculates a relative rotation angle of the optical scale 11HT withrespect to the optical sensor 35BT, and calculates rotationaldisplacements of the first rotating shaft 110A and the second rotatingshaft 110B.

With this structure, the optical sensors detect the rotational angles ofa plurality of respective optical scales that are caused to rotate asthe first and second rotating shafts are rotated, respectively, usingthe polarizations of the transmissive light or reflected light thussplit. Therefore, the torque detection apparatus can reduce theinfluence of fluctuations in the amount of detected light caused byforeign substances or the like, compared with when the light intensityof the transmissive light is directly detected, even when used areoptical torque sensors. Because the tolerance of foreign substances isincreased, the torque detection apparatus can be used in an increasednumber of environments. Furthermore, the torque detection apparatus canreduce the influence of fluctuations in the amount of detected light dueto precisions in the optical path (the distance from the optical scaleto the optical sensor), even when used are optical torque sensors. As aresult, the arrangement of the light sources and the optical sensors canbe designed more freely. In this manner, the torque sensors in thetorque detection apparatus can be reduced in size. Furthermore, thetorque detection apparatus can also achieve a higher resolution,compared with a magnetic torque sensor.

Ninth Embodiment

FIG. 45 is a schematic of a structure of an electric power steeringapparatus according to a ninth embodiment of the present invention. Themembers that are the same as those described above are assigned with thesame reference numerals, and redundant explanations thereof are omittedhereunder.

This electric power steering apparatus 80 includes a steering wheel 81,a steering shaft 82, a steering force assisting mechanism 83, auniversal joint 84, a lower shaft 85, another universal joint 86, apinion shaft 87, a steering gear 88, and a tie rod 89, in the order inwhich a force given by a steerer is communicated. The electric powersteering apparatus 80 also includes an electronic control unit (ECU) 90,a torque sensor 91 a, and a speed sensor 91 v. The computing unit 3described above may function as the ECU 90, or may be providedseparately from the ECU 90.

The steering shaft 82 includes an input shaft 82 a and an output shaft82 b. One end of the input shaft 82 a is connected to the steering wheel81, and the other end is connected to the steering force assistingmechanism 83 via the torque sensor 91 a. One end of the output shaft 82b is connected to the steering force assisting mechanism 83, and theother end is connected to the universal joint 84. In the embodiment, theinput shaft 82 a and the output shaft 82 b are made of a magneticmaterial such as iron.

One end of the lower shaft 85 is connected to the universal joint 84,and the other end is connected to the universal joint 86. One end of thepinion shaft 87 is connected to the universal joint 86, and the otherend is connected to the steering gear 88.

The steering gear 88 includes a pinion 88 a and a rack 88 b. The pinion88 a is connected to the pinion shaft 87. The rack 88 b is engaged withthe pinion 88 a. The steering gear 88 is structured as a rack andpinion. The rack 88 b in the steering gear 88 converts the rotatingmovement communicated to the pinion 88 a into a linear movement. The tierod 89 is connected to the rack 88 b.

The steering force assisting mechanism 83 includes a decelerator 92 anda brushless motor 101. The decelerator 92 is connected to the outputshaft 82 b. The brushless motor 101 is connected to the decelerator 92,and is a motor for generating an assisting steering torque. In theelectric power steering apparatus 80, the steering shaft 82, the torquesensor 91 a, and the decelerator 92 form a steering column. Thebrushless motor 101 applies an assisting steering torque to the outputshaft 82 b in the steering column. In other words, the electric powersteering apparatus 80 according to the embodiment is a column-assistedsteering apparatus. The brushless motor 101 may also be a motor with abrush, as long as such a motor is a rotary motor.

The torque sensor described in the earlier embodiments can be used asthe torque sensor 91 a. The torque sensor 91 a detects the steeringforce of the driver communicated via the steering wheel 81 to the inputshaft 82 a as a steering torque. The speed sensor 91 v detects therunning speed of a vehicle on which the electric power steeringapparatus 80 is mounted. The ECU 90 is electrically connected to thebrushless motor 101, the torque sensor 91 a, and the speed sensor 91 v.

The ECU 90 controls the operation of the brushless motor 101. The ECU 90acquires a signal from each of the torque sensor 91 a and the speedsensor 91 v. In other words, the ECU 90 acquires the steering torque Tfrom the torque sensor 91 a, and acquires the running speed Vb of thevehicle from the speed sensor 91 v. To the ECU 90, a power is suppliedfrom a power supply unit (e.g., buttery on the vehicle) 99 while anignition switch 98 is turned ON. The ECU 90 calculates an assistingsteering command value for an assisting command, based on the steeringtorque T and the running speed Vb. The ECU 90 adjusts a power X to besupplied to the brushless motor 101 based on the assisting steeringcommand value thus calculated. The ECU 90 acquires information of aninductive voltage from the brushless motor 101 as operation informationY.

The steering force of the steerer (driver) input to the steering wheel81 is communicated via the input shaft 82 a to the decelerator 92 in thesteering force assisting mechanism 83. At this time, the ECU 90 acquiresthe steering torque T input to the input shaft 82 a from the torquesensor 91 a, and acquires the running speed Vb from the speed sensor 91v. The ECU 90 then controls the operation of the brushless motor 101.The assisting steering torque generated by the brushless motor 101 iscommunicated to the decelerator 92.

The steering torque (including the assisting steering torque) output viathe output shaft 82 b is communicated to the lower shaft 85 via theuniversal joint 84, and further communicated to the pinion shaft 87 viathe universal joint 86. The steering force communicated to the pinionshaft 87 is communicated to the tie rod 89 via the steering gear 88,whereby causing a steered wheel to rotate.

As described earlier, in the electric power steering apparatus 80, thefirst rotating shaft and the second rotating shaft of the torque sensoraccording to the embodiment are mounted on the steering shaft so thatthe torque detection apparatus 200 can detect the steering torque.

With this structure, the optical sensor can detect a change in thepolarization direction of the transmissive light or the reflected lightin a manner less affected by foreign substances. In this manner, thereliability of the electric power steering apparatus can be improved.

Tenth Embodiment

FIG. 46 is a schematic of a structure of a robot arm according to atenth embodiment of the present invention. The members that are the sameas those described above are assigned with the same reference numerals,and redundant explanations thereof are omitted hereunder. This robot arm60 includes an arm 62 and an arm 63, in the order in which a force givenby a driving force 61 is communicated. The robot arm 60 also includes atorque sensor 91 b and a torque sensor 91 c.

As the torque sensor 91 b and the torque sensor 91 c, the torque sensorexplained above in the embodiments can be used. The torque sensor 91 billustrated in FIG. 46 can detect the torque communicated from thedriving force 61 to the arm 62. The torque sensor 91 c can detect thetorque communicated from the arm 62 to the arm 63.

Modification

FIG. 47 is a schematic of a structure of a robot arm according to amodification of the tenth embodiment. The members that are the same asthose described above are assigned with the same reference numerals, andredundant explanations thereof are omitted hereunder. This robot arm 60Aincludes an arm 64 and an arm 65, in an order in which an applied forceis communicated. The robot arm 60A is provided with a torque sensor 91d. The torque sensor 91 d can detect the torque communicated from thearm 64 to the arm 65.

As explained above, the torque detection apparatus according to theembodiment can calculate the torque applied to a joint in the robot arm.

Eleventh Embodiment

FIG. 48 is a schematic for explaining an optical sensor according to aneleventh embodiment of the present invention. The members that are thesame as those described above are assigned with the same referencenumerals, and redundant explanations thereof are omitted hereunder. Asillustrated in FIG. 48, four optical sensors 35 are arranged around asensor arrangement center 36R. A sensor arrangement axis passing throughthe sensor arrangement center 36R and extending from 36X− to 36X+intersects with a sensor arrangement axis passing through the sensorarrangement center 36R and extended from 36Y− to 36Y+. The four opticalsensors 35 are arranged symmetrically with respect to the sensorarrangement axes.

Even if the sensor arrangement center 36R is designed to be irradiatedwith the reflected light or the transmissive light from the light source41, some fluctuations might cause the position irradiated with the lightto deviate. In such a case, by comparing the outputs from the fouroptical sensors 35 arranged symmetrically with respect to the sensorarrangement axes, it is possible to recognize in which direction, thatis, toward which one of four quadrants defined by the sensor arrangementaxes extending from 36X− to 36X+ and extending from 36Y− to 36Y+, theposition irradiated with the reflected light or the transmissive lightfrom the light source 41 is deviated with respect to the sensorarrangement center 36R. Therefore, the optical axis of the reflectedlight or the transmissive light from the light source 41 can be adjustedto improve the precision of the optical encoder or the torque sensordescribed above.

Twelfth Embodiment

FIG. 49 is a schematic for explaining an optical sensor according to atwelfth embodiment of the present invention. The members that are thesame as those described above are assigned with the same referencenumerals, and redundant explanations thereof are omitted hereunder. Asillustrated in FIG. 49, this optical sensor 35 includes the firstoptical sensor 36A and the second optical sensor 36B. The first opticalsensor 36A is provided with the electrode base 36KA, a sensor base 36Kaconnected to the electrode base 36KA, and a first photoreceiver 36 a,and is capable of detecting the intensity of light with the firstpolarization direction. The first photoreceiver 36 a is provided withthe first polarizing layer that splits incident light to the light withthe first polarization direction, and receives the first polarized lightsplit by the first polarizing layer.

The second optical sensor 36B includes the electrode base 36KB, thesensor base 36Kb connected to the electrode base 36KB, and the secondphotoreceiver 36 b, and is capable of detecting the intensity of lightwith the second polarization direction. The second photoreceivers 36 bis provided with the second polarizing layer that splits the incidentlight to the light with the second polarization direction, and receivesthe second polarized light split by the second polarizing layer.

Each of the first photoreceiver 36 a and the second photoreceiver 36 bhas a spiral shape interlocking with each other, provided alternatinglyand spaced uniformly with each other by a given distance 36 w, asillustrated in FIG. 49.

With this structure, even when a foreign substance blocks a part of thesensing area, for example, the chances of the first photoreceiver 36 aand the second photoreceiver 36 b being blocked by approximately thesame degree can be increased, so that the possibility of the signalintensity output from one of the first photoreceiver 36 a and the secondphotoreceiver 36 b dropping extremely can be reduced. Therefore, evenwhen the intensity of the incident light is decreased by a foreignsubstance, the optical sensor 35 can detect a change in the polarizationdirection Pm via the differential signal V, in a manner less affected byforeign substances.

FIG. 50 is a schematic for explaining an exemplary modification of theoptical sensor according to the twelfth embodiment. The members that arethe same as those described above are assigned with the same referencenumerals, and redundant explanations thereof are omitted hereunder. Asillustrated in FIG. 50, the electrode base 36KA is arranged in a mannerextending in a direction perpendicular to the direction in which theelectrode base 36KB extends. The first photoreceiver 36 a extends in adirection perpendicular to the direction in which the electrode base36KA extends, and is bent in the middle, in the direction approachingthe electrode base 36KB. The second photoreceiver 36 b extends in adirection perpendicular to the direction in which the electrode base36KB extends, and is bent in the middle, in the direction approachingthe electrode base 36KA. Each of the first photoreceiver 36 a and thesecond photoreceiver 36 b is disposed in a manner interlocking eachother, provided alternatingly and spaced uniformly with each other by agiven distance 36 w. The optical sensor according to the modification ofthe twelfth embodiment has the same advantageous effect as that opticalsensor 35 according to the first embodiment and the twelfth embodiment.

Thirteenth Embodiment

FIG. 51 is a flowchart for explaining an optical sensor manufacturingprocess according to a thirteenth embodiment of the present invention.FIGS. 52-1 to 52-5 are schematics for explaining the optical sensormanufacturing process according to the thirteenth embodiment. FIGS. 52-1to 52-5 are partial cross-sectional views for explaining the process ofmanufacturing the Q-Q cross section in FIG. 15-1. The members that arethe same as those described above are assigned with the same referencenumerals, and redundant explanations thereof are omitted hereunder. Theoptical sensor manufacturing process will now be explained withreference to FIGS. 15-1, 51, and 52-1 to 52-5.

As illustrated in FIG. 51, to begin with, the manufacturing equipmentprepares an n-type silicon substrate 34, as illustrated in FIG. 52-1(Step S11). In the n-type silicon substrate 34 illustrated in FIG. 52-1,a base silicon substrate 34B which is a substrate surface 34 of thesilicon substrate 34 has an n+ layer doped with many donors.

As illustrated in FIG. 52-2, the manufacturing equipment then performs aresist patterning process in which patterning is performed to asubstrate surface 34A using a resist pattern 34Q of photoresists so asto achieve the shapes of the first photoreceivers 36 a and the secondphotoreceivers 36 b illustrated in FIG. 15-1 (Step S12).

The manufacturing equipment then performs a doping process in which thesubstrate surface 34A is doped with an element such as B or In (StepS13). As illustrated in FIG. 52-3, P-type semiconductor photoreceivers37 are formed on the substrate surface 34A.

As illustrated in FIG. 52-4, the manufacturing equipment then removesthe resist pattern 34Q, and performs an insulating process in which thesubstrate surface 34A is covered by an insulating layer 38 b that isAl₂O₃ or SiO₂, for example (Step S14). The insulating layer 38 b is madeof a material having translucency. Through the manufacturing processdescribed above, a photoreceiver body 35U of the optical sensor 35 isprovided.

As illustrated in FIG. 52-5, the manufacturing equipment then performs afirst polarizing layer forming process in which the first polarizinglayer 39 a is formed at positions corresponding to the firstphotoreceivers 36 a illustrated in FIG. 15-1 (Step S15). The firstpolarizing layer 39 a may be formed using a photo-induced polarizinglayer or a wire grid pattern in which wires are arranged in parallel,for example. In this manner, as illustrated in FIG. 52-5, the firstpolarizing layer 39 a is formed on every two photoreceivers 37.

The manufacturing equipment then performs a second polarizing layerforming process in which the second polarizing layer 39 b is formed atpositions corresponding to the second photoreceivers 36 b illustrated inFIG. 15-1 (Step S16). The second polarizing layer 39 b may be formedusing a photo-induced polarizing layer or a wire grid pattern in whichwires are arranged in parallel, for example. In this manner, asillustrated in FIG. 52-5, the second polarizing layer 39 b is formed onevery two photoreceivers 37. The manufacturing equipment then performsan electrode forming process in which the electrode base 36KA and theelectrode base 36KB illustrated in FIG. 15-1 are formed using aconductive material such as Au or Al so that electricity can beconducted to the first photoreceivers 36 a and the second photoreceivers36 b through respective through-holes not illustrated that are formedthrough the insulator 38 b (Step S17).

As explained above, the method for manufacturing an optical sensorincludes the photoreceiver forming process and the polarizing layerforming process. In the photoreceiver forming process, photoreceiversare formed on the surface of the silicon substrate 34 in such a mannerthat the first photoreceivers 36 a and the second photoreceivers 36 breceiving light are arranged alternatingly and spaced uniformly witheach other. In the polarizing layer forming process, the firstpolarizing layer 39 a for splitting the incident light into the firstpolarized light with the first polarization direction is provided on topof the first photoreceivers 36 a so that the first polarized lightbecomes incident on the first photoreceivers 36 a, and the secondpolarizing layer 39 b for splitting the incident light into the secondpolarized light with the second polarization direction is provided ontop of the second photoreceivers so that the second polarized lightbecomes incident on the second photoreceivers 36 b.

Modification of Optical Sensor Manufacturing Process

FIGS. 53-1 to 53-3 are schematics for explaining manufacturing of apolarizing layer in the optical sensor manufacturing process accordingto a modification of the thirteenth embodiment. The members that are thesame as those described above are assigned with the same referencenumerals, and redundant explanations thereof are omitted hereunder.Through Steps S11, S12, S13, and S14 illustrated in FIG. 51, thephotoreceiver body 35U of the optical sensor 35 illustrated in FIG. 53-3is achieved.

As illustrated in FIG. 53-1, the manufacturing equipment then prepares atranslucent substrate 39B that allows light to pass through. Asillustrated in FIG. 53-2, the manufacturing equipment performs a firstpolarizing layer forming process in which the first polarizing layer 39a is formed at positions corresponding to the first photoreceivers 36 aillustrated in FIG. 15-1 on the translucent substrate 39B allowing lightto pass through (Step S15). The first polarizing layer 39 a may beformed using a photo-induced polarizing layer or a wire grid pattern inwhich wires are arranged in parallel, for example.

The manufacturing equipment then performs a second polarizing layerforming process in which the second polarizing layer 39 b is formed atpositions corresponding to the second photoreceivers 36 b illustrated inFIG. 15-1 (Step S16). The second polarizing layer 39 b may be formedusing a photo-induced polarizing layer or a wire grid pattern in whichwires are arranged in parallel, for example. In this manner, the secondpolarizing layer 39 b is formed on every two photoreceivers 37, asillustrated in FIG. 53-2. The translucent substrate 39B is then mountedon and fixed to the insulator 38 b in the photoreceiver body 35U of theoptical sensor 35, as illustrated in FIG. 53-3. The insulator 38 b andthe translucent substrate 39B are adjusted to thicknesses not causinglight to attenuate.

The manufacturing equipment then performs an electrode forming processin which the electrode base 36KA and the electrode base 36KB are formedusing a conductive material such as Au or Al so that the electricity canbe conducted to the first photoreceivers 36 a and the secondphotoreceivers 36 b illustrated in FIG. 15-1 through the respectivethrough-holes (not illustrated) formed through the translucent substrate39B and the insulator 38 b (Step S17). The manufacturing equipment mayperform the electrode forming process (Step S17) before performing thefirst polarizing layer forming process (Step S15) and the secondpolarizing layer forming process (Step S16).

As explained above, the method for manufacturing an optical sensorincludes the photoreceiver forming process and the polarizing layerforming process. In the photoreceiver forming process, photoreceiversare formed on the surface of the silicon substrate 34 in such a mannerthat the first photoreceivers 36 a and the second photoreceivers 36 breceiving light are arranged alternatingly and spaced uniformly witheach other. In the polarizing layer forming process, the firstpolarizing layer 39 a for splitting the incident light into the firstpolarized light with the first polarization direction is provided on topof the first photoreceivers 36 a so that the first polarized lightbecomes incident on the first photoreceivers 36 a, and the secondpolarizing layer 39 b for splitting the incident light into the secondpolarized light with the second polarization direction is provided ontop of the second photoreceivers so that the second polarized lightbecomes incident on the second photoreceivers 36 b. In the polarizinglayer forming process, using the silicon substrate 34 as a firstsubstrate, the first polarizing layer 39 a and the second polarizinglayer 39 b are formed on the surface of the translucent substrate 39Bwhich is the second substrate, and the second substrate is bonded ontothe first substrate. The first polarizing layer 39 a is then aligned ina manner overlapping with the corresponding first photoreceiver 36 a,and the second polarizing layer 39 b is aligned in a manner overlappingwith the corresponding second photoreceiver 36 b.

Another Modification of Optical Sensor Manufacturing Process

FIGS. 54-1 and 54-2 are schematics for explaining manufacturing of thepolarizing layer in the optical sensor manufacturing process accordingto another modification of the thirteenth embodiment. FIG. 55 is aschematic for explaining an example of the optical sensor according tothe thirteenth embodiment. The members that are the same as thosedescribed above are assigned with the same reference numerals, andredundant explanations thereof are omitted hereunder. Through Steps S11,S12, S13, and S14 illustrated in FIG. 51, the photoreceiver body 35U ofthe optical sensor 35 illustrated in FIG. 53-3 is achieved.

As illustrated in FIG. 54-1, the manufacturing equipment preparestranslucent substrates 39C and 39D allowing light to pass through. Themanufacturing equipment then performs the first polarizing layer formingprocess in which the first polarizing layer 39 a is formed at positionscorresponding to the first photoreceivers 36 a illustrated in FIG. 15-1on the translucent substrate 39D (Step S15). The first polarizing layer39 a may be formed using a photo-induced polarizing layer or a wire gridpattern in which wires are arranged in parallel, for example.

The manufacturing equipment then performs a second polarizing layerforming process in which the second polarizing layer 39 b is formed atpositions corresponding to the second photoreceivers 36 b illustrated inFIG. 15-1 on the side of the translucent substrate 39C facing thetranslucent substrate 39D (Step S16). The second polarizing layer 39 bmay be formed using a photo-induced polarizing layer or a wire gridpattern in which wires are arranged in parallel, for example. Asillustrated in FIG. 54-2, the translucent substrate 39C and thetranslucent substrate 39D are then laminated. The translucent substrate39D is then mounted on and fixed to the insulator 38 b in thephotoreceiver body 35U of the optical sensor 35. The insulator 38 b andthe translucent substrates 39C, 39D are adjusted to thicknesses notcausing light to attenuate. In this manner, the second polarizing layer39 b is formed on every two photoreceivers 37 and the first polarizinglayer 39 a is formed on the other every two photoreceivers 37, asillustrated in FIG. 55.

The manufacturing equipment then performs the electrode forming processin which the electrode base 36KA and the electrode base 36KB illustratedin FIG. 55 are formed using a conductive material such as Au or Al sothat the electricity can be conducted to the first photoreceivers 36 aand the second photoreceivers 36 b through the respective through-holes(not illustrated) formed through the translucent substrates 39C and 39Dand the insulator 38 b (Step S17). The manufacturing equipment mayperform the electrode forming process (Step S17) before performing thefirst polarizing layer forming process (Step S15) and the secondpolarizing layer forming process (Step S16).

As explained above, the method for manufacturing an optical sensorincludes the photoreceiver forming process and the polarizing layerforming process. In the photoreceiver forming process, photoreceiversare formed on the surface of the silicon substrate 34 in such a mannerthat the first photoreceivers 36 a and the second photoreceivers 36 breceiving light are arranged alternatingly and spaced uniformly witheach other. In the polarizing layer forming process, the firstpolarizing layer 39 a for splitting the incident light into the firstpolarized light with the first polarization direction is provided on topof the first photoreceivers 36 a so that the first polarized lightbecomes incident on the first photoreceivers 36 a, and the secondpolarizing layer 39 b for splitting the incident light into the secondpolarized light with the second polarization direction is provided ontop of the second photoreceivers so that the second polarized lightbecomes incident on the second photoreceivers 36 b. In the polarizinglayer forming process, using the silicon substrate 34 as the firstsubstrate, the first polarizing layer 39 a is formed on the surface ofthe translucent substrate 39D which is the second substrate, and thesecond polarizing layer 39 b is formed on the surface of the translucentsubstrate 39C which is a third substrate. The second substrate and thethird substrate are then bonded onto the first substrate, and the firstpolarizing layer 39 a is aligned in a manner overlapping with thecorresponding first photoreceiver 36 a, and the second polarizing layer39 b is aligned in a manner overlapping with the corresponding secondphotoreceiver 36 b.

Fourteenth Embodiment

FIG. 56 is a flowchart for explaining an optical sensor packagemanufacturing process according to a fourteenth embodiment of thepresent invention. FIGS. 57-1 to 57-6 are schematics for explaining theoptical sensor package manufacturing process according to the fourteenthembodiment. FIG. 58 is a plan view for explaining an aperture on theoptical sensor according to the fourteenth embodiment. The opticalsensor package 31 illustrated in FIG. 2-2 is manufactured by packagingthe optical sensor 35. The members that are the same as those describedabove are assigned with the same reference numerals, and redundantexplanations thereof are omitted hereunder. The optical sensormanufacturing process will now be explained with reference to FIGS. 56,57-1 to 57-6, and 58.

As illustrated in FIG. 56, to begin with, the manufacturing equipmentprepares a sensor substrate 31K made of glass, quartz (SiO₂), silicon, aprinted substrate, or a film material, as illustrated in FIG. 57-1 (StepS21). The sensor substrate 31K illustrated in FIG. 57-1 includes a basesubstrate 31F, a penetrating conductive layer 31H embedded in eachthrough-hole SH penetrating through the surfaces of the base substrate31F, and external electrodes 31P that are electrically connected to thepenetrating conductive layer 31H.

As illustrated in FIG. 57-2, the manufacturing equipment then performsan implementing process in which the optical sensors 35 are implementedon one surface of the sensor substrate 31K (Step S22).

As illustrated in FIG. 57-3, the manufacturing equipment then performsan electrically connecting process in which a conductive connection viaa bonding wire 31W is established between each of the optical sensors 35and the corresponding penetrating conductive layers 31H (Step S23). Theelectrical connection is not limited to wire bonding via bonding wires31W, as long as such a conductive connection between the optical sensor35 and the penetrating conductive layer 31H is ensured.

As illustrated in FIG. 57-4, the manufacturing equipment then performs acapping process in which the optical sensors 35 are protected withencapsulation resin 31M (Step S24). The encapsulation resin 31M is atranslucent insulating material.

As illustrated in FIG. 57-5, the manufacturing equipment then performs aprocess of forming a light-shielding film 31R on the surface of theencapsulation resin 31M with a light-shielding material such as a blackresist, a synthetic resin, paint, or a metal film (Step S25). Becausethe light-shielding film 31R serves as a stop for the incident light,the light-shielding film 31 is formed in a manner not overlapping withthe first photoreceivers 36 a and the second photoreceivers 36 b in theoptical sensor 35 in a plan view. The optical sensor 35 can adjust theamount of incident light using the light-shielding film 31R, so that thereachable range of the incident light is adjusted. As a result, theoptical sensor 35 can detect a change in the polarization direction ofthe transmissive light or the reflected light highly accurately.

The manufacturing equipment then performs a dicing process in which thesensor substrate 31K is cut across dicing lines DS illustrated in FIG.57-5 (Step S26). The sensor substrate 31K is then separated into eachpackage illustrated in FIG. 57-6. In this manner, the optical sensorpackage 31 is manufactured.

As illustrated in FIGS. 57-6 and 58, to allow the optical sensor 35 toreceive light, an aperture 31T surrounded by the light-shielding film31R is provided, so that the optical sensor 35 can receive incidentlight passing through the aperture 31T. The aperture 31T is illustratedto have a round shape in FIG. 58, as an example, but may also have arectangular shape.

Modification of Optical Sensor Package Manufacturing Process

FIGS. 59-1 to 59-6 are schematics for explaining an optical sensorpackage manufacturing process according to the fourteenth embodiment.The members that are the same as those described above are assigned withthe same reference numerals, and redundant explanations thereof areomitted hereunder. The modification of the optical sensor manufacturingprocess will now be explained with reference to FIGS. 56, 58, and 59-1to FIG. 59-6.

As illustrated in FIG. 56, to begin with, the manufacturing equipmentprepares the sensor substrate 31K illustrated in FIG. 59-1 (Step S21).The sensor substrate 31K illustrated in FIG. 59-1 includes the basesubstrate 31F, a penetrating conductive layer 31H embedded in thethrough-holes SH penetrating through the surfaces of the base substrate31F, and external electrodes 31P that are electrically connected to thepenetrating conductive layer 31H.

As illustrated in FIG. 59-2, the manufacturing equipment then performsan implementing process in which the optical sensors 35 are implementedon one surface of the sensor substrate 31K (Step S22).

As illustrated in FIG. 59-3, the manufacturing equipment then performsan electrically connecting process for establishing a conductiveconnection between each of the optical sensors 35 and the penetratingconductive layer 31H using bonding wires 31W (Step S23). The electricalconnection is not limited to wire bonding using bonding wires 31W, aslong as a conductive connection between each of the optical sensors 35and the penetrating conductive layer 31H can be ensured.

As illustrated in FIGS. 59-4 and 59-5, the manufacturing equipment thenperforms a capping process in which the optical sensor 35 is protectedwith a wall member 311 and a cap substrate 31G (Step S24). The wallmember 311 and the cap substrate 31G are made of glass, silicon, aceramic, or an insulating material. By covering the wall member 311 bythe cap substrate 31G under a nitrogen atmosphere or a vacuumatmosphere, an internal space 31Q of the optical sensor package 31 canbe nitrogen-sealed or vacuum-sealed. As a result, the space surroundingthe optical sensor 35 is kept clean, so that the optical sensor 35 isless affected by foreign substances or the like.

As illustrated in FIG. 59-5, the manufacturing equipment then performs aprocess of forming the light-shielding film 31R on the surface of thecap substrate 31G with a light-shielding material such as a blackresist, a synthetic resin, paint, or a metal film (Step S25). Becausethe light-shielding film 31R serves as a stop for the incident light, inthe manner described later, the light-shielding film 31R is formed in amanner not overlapping with the first photoreceivers 36 a and the secondphotoreceivers 36 b in the optical sensor 35 in a plan view.

The manufacturing equipment then performs a dicing process in which thesensor substrate 31K is cut across dicing lines DS illustrated in FIG.59-5 (Step S26). The sensor substrate 31K is then separated into eachdie, into the package as illustrated in FIG. 59-6. In this manner, theoptical sensor packages 31 are manufactured.

As illustrated in FIGS. 58 and 59-6, to allow the optical sensor 35 toreceive light, the aperture 31T surrounded by the light-shielding film31R is provided, so that the optical sensor 35 can receive incidentlight passing through the aperture 31T. The aperture 31T is illustratedto have a round shape in FIG. 58, as an example, but may also have arectangular shape.

Fifteenth Embodiment

FIG. 60 is a plan view for explaining a light source according to afifteenth embodiment of the present invention. FIG. 61 is a plan viewfor explaining a light emitting portion of the light source according tothe fifteenth embodiment. The members that are the same as thosedescribed above are assigned with the same reference numerals, andredundant explanations thereof are omitted hereunder. The light source41 according to the embodiments described above is the same as a lightsource 41X illustrated in FIG. 60, and is a package of a light emittingdevice 41U such as a light-emitting diode, a laser light source such asa vertical-cavity surface-emitting laser, or a filament. In the lightemitting device 41U, a surface-emitting light source is used.

The light source 41X includes a base substrate 41F, a penetratingconductive layer 41H embedded in the through-holes SH, externalelectrodes 41P that are electrically connected to the penetratingconductive layer 41H, the light emitting device 41U implemented on thebase substrate 41F, bonding wires 41W that establish conductiveconnections between the light emitting device 41U and the respectivepenetrating conductive layers 41H, encapsulation resin 41M that protectsthe light emitting device 41U, and a light-shielding film 41R.

In the light source 41X, the light-shielding film 41R functions as astop for the light source light 71 that limits the light source light 71emitted from the light emitting device 41U illustrated in FIGS. 60 and61 to the size of a light emitting portion 41T.

FIG. 62 is a plan view for explaining an exemplary modification of thelight source according to the fifteenth embodiment. A light source 41Yillustrated in FIG. 62 has a light emitting portion 41TL with a convexsurface, compared with the light emitting portion 41T of the lightsource 41X, and the convex shape of the surface serves as a collimatelens that converts the light source light 71 emitted from the lightemitting device 41U into parallel rays, or as a condensing lens. Withthis structure, the light source 41Y can emit the light source light 71having a uniform light intensity distribution.

FIG. 63 is a plan view for explaining another modification of the lightsource according to the fifteenth embodiment. This light source 41Zillustrated in FIG. 63 has a light emitting portion 41TP in acylindrical shape, compared with the light emitting portion 41T of thelight source 41X, and the internal cylindrical body serves as a lightpipe so that the light source light 71 emitted from the light emittingdevice 41U is passed through the light pipe as a waveguide. With thisstructure, the light source 41Z can emit the light source light 71having a uniform light intensity distribution.

FIGS. 64, 65, 66, and 67 are plan views for explaining waveguides forguiding the light from the light source according to the fifteenthembodiment. In the light source 41Z illustrated in FIG. 63, the lightpipe is integrated with a package, but the light source may beconfigured as an optical system. For example, in this optical system41V1, the light source 41Y, a light pipe LP1, a scattering plate SQ, anda slit SL that is a gap formed between a plurality of shielding platesAP are arranged in line, as illustrated in FIG. 64. The scattering plateSQ and the shielding plates AP, which are described later, may not beprovided. The scattering plate SQ allows the light passing through thescattering plate SQ to be scattered so that the illuminance unevennesscan be reduced. The light pipe LP1 is a cylindrical member made of amaterial such as a resin material including acrylic, glass, or quartz.The cross section of the light pipe LP1 may have a circular shape or apolygonal shape. As another example, this optical system 41V2 may bebent as the light pipe LP2 illustrated in FIG. 65. As another example,this optical system 41V3 may be bent in a U shape as the light pipe LP3illustrated in FIG. 66. The light pipe LP2 and the light pipe LP3 canimprove the freedom in positions where the light source Y is arranged.

An optical system 41V4 illustrated in FIG. 67 includes the light source41Y, a plate-shaped waveguide plate LP4, and a scattering plate SQ. Inthis optical system 41V4, the light source 41Y is covered by a reflectorRF, so that the light source light 71 from the light source 41Y becomesincident on a side surface of the waveguide plate LP4. A mirror surfaceML provided on one side of the waveguide plate LP4 and having recessesand protrusions changes the direction of the light source light 71 thatis incident on the side surface of the waveguide plate LP4 to adirection in which the light source light 71 is output vertically fromthe surface of the waveguide plate LP4. With this structure, the opticalsystem 41V4 can emit the light source light 71 having a uniform lightintensity distribution.

Process of Manufacturing Light Source Package

FIG. 68 is a flowchart for explaining a light source packagemanufacturing process according to the fifteenth embodiment. FIGS. 69-1to 69-6 are schematics for explaining the light source packagemanufacturing process according to the fifteenth embodiment. The membersthat are the same as those described above are assigned with the samereference numerals, and redundant explanations thereof are omittedhereunder. The process of manufacturing the light source 41Y will now beexplained with reference to FIGS. 62, 68, 69-1 to 69-6.

As illustrated in FIG. 68, to begin with, the manufacturing equipmentprepares a light source substrate 41K illustrated in FIG. 69-1 (StepS31). The light source substrate 41K illustrated in FIG. 69-1 includesthe base substrate 41F, the penetrating conductive layer 41H embedded inthe through-holes SH penetrating through the surfaces of the basesubstrate 41F, and the external electrodes 41P that are electricallyconnected to the penetrating conductive layer 41H.

As illustrated in FIG. 69-2, the manufacturing equipment then performsan implementing process in which the light emitting devices 41U areimplemented on one surface of the light source substrate 41K (Step S32).

As illustrated in FIG. 69-3, the manufacturing equipment then performsan electrically connecting process in which a conductive connection viaa bonding wire 41W is established between each of the light emittingdevices 41U and the penetrating conductive layer 41H (Step S33). Theelectrical connection is not limited to wire bonding via a bonding wire41W, as long as a conductive connection between the light emittingdevice 41U and the penetrating conductive layer 41H can be ensured.

As illustrated in FIG. 69-4, the manufacturing equipment then performs acapping process in which the light emitting device 41U is protectedusing the encapsulation resin 41M (Step S34). The encapsulation resin41M is a translucent insulating material.

As illustrated in FIG. 69-5, the manufacturing equipment then performsthe process of forming the light-shielding film 41R on the surface ofthe encapsulation resin 41M, with a light-shielding material such as ablack resist, a synthetic resin, paint, or a metal film (Step S35).

The manufacturing equipment then performs an optical member process inwhich the light emitting portions 41TL illustrated in FIG. 69-6 areformed (Step S36). The light emitting portions 41TL are formed bymold-crimping using the same material as the encapsulation resin 41M,for example.

The manufacturing equipment then performs a dicing process in which thelight source substrate 41K illustrated in FIG. 69-6 is cut across thedicing lines DS (Step S37). The light source substrate 41K is thenseparated into each die, into each package illustrated in FIG. 62. Inthis manner, the light source 41Y is manufactured.

FIG. 70 is a schematic for explaining shielding of the light sourceaccording to the fifteenth embodiment. The light source light 71 fromthe light source 41 is output toward the optical scale 11 through theslit SL that is a gap between the shielding plates AP. A sensing area71X on the optical scale 11 is dependent on the shape of the slit SL.Therefore, by changing the shape and the arrangement of the shieldingplates AP, the sensing area 71X can be changed as appropriate. Thesensing area 71X on the optical scale 11 corresponds to a detection area72X of the optical sensor.

FIGS. 71 and 72 are schematics for explaining light sources with ahigher shielding efficiency according to the fifteenth embodiment. Eachof light sources 41Y1 and 41Z1 illustrated in FIGS. 71 and 72,respectively, is integrated with shielding plates 41AP, and theshielding plates 41AP allow the light source light 71 to focus to agiven shape. The sensing area 71X is thus defined.

Sixteenth Embodiment

FIG. 73 is a flowchart for explaining an optical scale manufacturingprocess according to a sixteenth embodiment of the present invention.FIGS. 74-1 to 74-7 are schematics for explaining the optical scalemanufacturing process according to the sixteenth embodiment. The membersthat are the same as those described above are assigned with the samereference numerals, and redundant explanations thereof are omittedhereunder. FIGS. 74-1 to 74-7 are partial cross-sectional views of theoptical scale 11 illustrated in FIG. 4 during the manufacturing process.The process of manufacturing the optical scale 11 according to thesixteenth embodiment using nanoimprinting will now be explained withreference to FIGS. 4, 73, and 74-1 to 74-7.

As illustrated in FIG. 73, to begin with, the manufacturing equipmentprepares a base substrate 11 be made of glass, quartz (SiO₂), silicon, aprinted substrate, or a film material, as illustrated in FIG. 74-1 (StepS41). A resist layer 11 r such as polymethyl methacrylate (PMMA) orpolyimide resin is applied on the surface of the base substrate 11 be,with a seed layer 11 se interposed between the resist layer 11 r andbase substrate 11 be, as illustrated in FIG. 74-1. The seed layer 11 seis a multi-layered film that are a Cr layer and a Cu layer formed on thebase substrate 11 be, for example.

As illustrated in FIG. 74-2, the manufacturing equipment then performs ananoimprinting process in which a mold 11K made of a metal, asillustrated in FIG. 74-2, is pressed against the resist layer 11 r, sothat the recesses and protrusions in a size of 50 nanometers to 500nanometers engraved in the mold 11K is transferred onto the resist layer11 r as fine patterns 11 rp (Step S42). In the nanoimprinting process(Step S42), processes for forming the fine patterns 11 rp referred to asthermal nanoimprinting or UV nanoimprinting may be used. In the thermalnanoimprinting, the resist layer 11 r is heated, whereas the resistlayer 11 r is irradiated with UV light in the UV nanoimprinting. Asillustrated in FIG. 74-3, the manufacturing equipment then performs amold removing process in which the mold 11K is removed from the resistlayer 11 r (Step S43). The resist layer 11 r after the transfer has aremaining film 11 rn as well as the fine patterns 11 rp. Therefore, themanufacturing equipment performs a remaining film process in whichunnecessary remaining film 11 rn is removed by reactive ion etching(RIE) as illustrated in FIG. 74-4 (Step S44).

The manufacturing equipment then performs a plating process in whichelectroplating is used to allow metal 11 m to be deposited on the seedlayer 11 se (Step S45). As illustrated in FIG. 74-5, the metal 11 m isdeposited in the space between the fine patterns 11 rp. The metal 11 mis a metal such as Ni, Cr, Al, Mo, Cu, or Au, or an alloy composed ofone or more these metals, for example,

As illustrated in FIG. 74-6, the manufacturing equipment then performs aresist removing process in which the resist on the fine patterns 11 rpis removed (Step S46). Once the resist on the fine patterns 11 rp isremoved, the pattern of wires limp formed by the metal 11 m remains.

As illustrated in FIG. 74-7, the manufacturing equipment then performs aseed layer etching process in which the seed layer 11 se between thewires limp is removed (Step S47). The seed layer etching process (StepS47) may be omitted if the seed layer 11 se is thin enough, so that theoptical characteristics of the optical scale 11 are not affected.

Through the manufacturing process described above, the manufacturingequipment can form the signal tracks T1 having the wires g referred toas a wire grid pattern and the transmissive area w through which theentire or a part of the light source light 71 is allowed to pass on theoptical scale 11.

Seventeenth Embodiment

FIG. 75 is a flowchart for explaining an optical scale manufacturingprocess according to a seventeenth embodiment of the present invention.FIGS. 76-1 to 76-6 are schematics for explaining the optical scalemanufacturing process according to the seventeenth embodiment. Themembers that are the same as those described above are assigned with thesame reference numerals, and redundant explanations thereof are omittedhereunder. FIGS. 76-1 to 76-6 are partial cross-sectional views of theoptical scale 11 illustrated in FIG. 4 during the manufacturing process.The process of manufacturing the optical scale 11 according to theseventeenth embodiment will now be explained with reference to FIGS. 4,75, and 76-1 to 76-6.

As illustrated in FIG. 75, to begin with, the manufacturing equipmentprepares a base substrate 11 be made of glass, quartz (SiO₂), silicon, aprinted substrate, or a film material, as illustrated in FIG. 76-1 (StepS51). As illustrated in FIG. 76-1, the resist layer 11 r such aspolymethyl methacrylate (PMMA) or polyimide resin is applied on thesurface of the base substrate 11 be.

As illustrated in FIG. 76-2, the manufacturing equipment then performs ananoimprinting process in which the mold 11K made of a metal, asillustrated in FIG. 76-2, is pressed against the resist layer 11 r, sothat the recesses and protrusions in a size of 50 nanometers to 500nanometers engraved in the mold 11K are transferred as fine patterns 11rp on the resist layer 11 r (Step S52). In the nanoimprinting process(Step S52), processes for forming the fine patterns 11 rp referred to asthermal nanoimprinting or UV nanoimprinting may be used. In the thermalnanoimprinting, the resist layer 11 r is heated, whereas the resistlayer 11 r is irradiated with UV light in the UV nanoimprinting. Asillustrated in FIG. 76-3, the manufacturing equipment then performs amold removing process in which the mold 11K is removed from the resistlayer 11 r (Step S53). The resist layer 11 r after the transfer has aremaining film 11 rn as well as the fine patterns 11 rp. Therefore, themanufacturing equipment performs remaining film processing in whichunnecessary remaining film 11 rn is removed by RIE, as illustrated inFIG. 76-4 (Step S54).

The manufacturing equipment then performs a vapor deposition process inwhich the metal 11 m is vapor-deposited in a manner covering the finepatterns 11 rp (Step S55). As illustrated in FIG. 76-5, the metal 11 mis provided in the space between the fine patterns 11 rp. A metal 11 mnis also vapor-deposited on the resist on the fine patterns 11 rp. Themetal 11 m is a metal such as Ni, Cr, Al, Mo, Cu, or Au, or an alloycomposed of one or more these metals. The vapor deposition is performedas vacuum deposition, sputtering, or vapor phase epitaxy (VPE).

As illustrated in FIG. 76-6, the manufacturing equipment then performs aresist removing process in which the resist on the fine patterns 11 rpis removed (Step S56). When the resist on the fine patterns 11 rp isremoved, the metal 11 mn on the resist illustrated in FIG. 76-5 issimultaneously lifted off, and the patterns of the metal 11 m (wire g)remain on the base substrate 11 be. Through the manufacturing processdescribed above, the manufacturing equipment can form a signal tracks T1having wires g which are referred to as a wire grid pattern, and thetransmissive area w through which the entire or a part of the lightsource light 71 is allowed to pass on the optical scale 11.

FIG. 77 is a schematic for explaining an example of the wire gridpattern on the optical scale according to the seventeenth embodiment.The manufacturing method described above results in an optical scale 11on which the metal 11 m is exposed from the surface of the basesubstrate 11 be, as illustrated in FIG. 77, for example. Therefore,foreign substances could become attached to the surfaces of the metal 11m.

FIGS. 78 to 86 are schematics for explaining an example of the wire gridpattern on the optical scale according to the seventeenth embodiment.The optical scale 11 illustrated in FIG. 78 includes the base substrate11 be, a spacer member 11 sp, and a cap substrate 11 cp. The spacermember 11 sp is provided in a manner standing from the base substrate 11be and surrounding the outer periphery of the base substrate 11 be. Thecap substrate 11 cp serves as a lid on the spacer member 11 sp, and themetal 11 m is surrounded by the base substrate 11 be, the spacer member11 sp, and the cap substrate 11 cp. The spacer member 11 sp and the capsubstrate 11 cp are made of glass, silicon, ceramic, an insulatingmaterial, or resin such as acrylic resin, for example. By covering thespacer member 11 sp with the cap substrate 11 cp under a nitrogenatmosphere or a vacuum atmosphere, an internal space 11Q surrounded bythe base substrate 11 be, the spacer member 11 sp, and the cap substrate11 cp can be nitrogen-sealed or vacuum-sealed. As a result, the spacesurrounding the metal 11 m (wire pattern) are kept clean on the opticalscale 11, so that the metal 11 m is less affected by foreign substancesor the like.

As illustrated in FIG. 79, the optical scale 11 may include a capsubstrate 11 cp also provided with the metal 11 m (wire pattern), andthe same wire patterns may be positioned and layered in a manner facingeach other. In this manner, the optical scale 11 may include multiplelayers of an arrangement of wires referred to as a wire grid pattern ina thickness direction in which the transmissive light 73 or thereflected light 72 become incident, so that a highly accurate opticalscale with a smaller error can be achieved.

As illustrated in FIG. 80, the optical scale 11 may also include a basesubstrate 11 be both sides of which are provided with the metal 11 m(wire pattern), and in which the same wire patterns are positionedfacing each other with the base substrate 11 be interposed between thewire patterns. In this manner, multiple layers of an arrangement ofwires referred to as a wire grid pattern can be arranged (layered) inthe optical scale 11 in the thickness direction in which thetransmissive light 73 or the reflected light 72 becomes incident, sothat a highly accurate optical scale with a smaller error can beachieved. The optical scale 11 illustrated in FIG. 80 includes the basesubstrate 11 be, spacer members 11 sp 1 and 11 sp 2, and cap substrates11 cp 1 and 11 cp 2. Each of the spacer members 11 sp 1 and 11 sp 2 isprovided in a manner standing from the corresponding surface of the basesubstrate 11 be. The cap substrates 11 cp 1 and 11 cp 2 surrounding theouter periphery of the base substrate 11 be serve as lids on therespective spacer members 11 sp 1 and 11 sp 2, so that the metal 11 m issurrounded by the base substrate 11 be, the spacer members 11 sp 1 and11 sp 2, and the cap substrates 11 cp 1 and 11 cp 2. The internal space11Q of the optical scale 11 may be nitrogen-sealed or vacuum-sealed. Theoptical scale 11 may also include cap substrates 11 cp 1 and 11 cp 2each of which is also provided with the metal 11 m (wire pattern), asillustrated in FIG. 81, and in which the same wire patterns arepositioned facing each other. In this manner, the optical scale 11 canbe provided with four layers of an arrangement of wires referred to as awire grid pattern in the thickness direction in which the transmissivelight 73 or the reflected light 72 becomes incident, so that a highlyaccurate optical scale with a smaller error can be achieved.

In the optical scale 11 illustrated in FIG. 82, the metal 11 m iscovered by a translucent protection layer 11 v allowing light to passthrough. Therefore, the space surrounding the metal 11 m (wire pattern)are kept clean on the optical scale 11, so that the metal 11 m is lessaffected by foreign substances or the like.

As illustrated in FIG. 83, the optical scale 11 may also include basesubstrates 11 be each provided with a pair of metal 11 m, and in whichthe same wire patterns are positioned facing each other with theprotection layer 11 v interposed between the wire patterns. In thismanner, the optical scale 11 can be provided with multiple layers of anarrangement of wires referred to as a wire grid pattern in the thicknessdirection in which the transmissive light 73 or the reflected light 72becomes incident, so that a highly accurate optical scale with a smallererror can be achieved.

As illustrated in FIG. 84, the optical scale 11 may also include a basesubstrate 11 be both sides of which are provided with the metal 11 m(wire pattern), and in which the same wire patterns are positionedfacing each other with the base substrate 11 be interposed between thewire patterns. In this optical scale 11, the metals 11 m are covered bytranslucent protection layers 11 v that pass through the light.Therefore, the space surrounding the metals 11 m (wire pattern) are keptclean on the optical scale 11, so that the metal 11 m is less affectedby foreign substances or the like.

In the optical scale 11 illustrated in FIG. 85, the optical scale 11illustrated in FIG. 84 is stacked in plurality, in the thicknessdirection in which the transmissive light 73 or the reflected light 72becomes incident. In this manner, the optical scale can be provided withfour layers of an arrangement of wires referred to as a wire gridpattern, in the thickness direction in which the transmissive light 73or the reflected light 72 becomes incident, so that a highly accurateoptical scale with a smaller error can be achieved.

The optical scale 11 illustrated in FIG. 86, an antireflection film 11ARis provided on each side of the optical scale illustrated in FIG. 82. Inthis manner, diffused reflections can be suppressed on the optical scale11. The antireflection film 11AR may also be provided to the surfaces ofthe optical scales 11 illustrated in FIGS. 78 to 85.

Eighteenth Embodiment

FIG. 87 is a schematic for explaining an optical scale according to aneighteenth embodiment of the present invention. FIGS. 88, 89, and 90 areschematics for explaining the polarizing axes in the optical sensoraccording to the eighteenth embodiment. The members that are the same asthose described above are assigned with the same reference numerals, andredundant explanations thereof are omitted hereunder.

This optical scale 11I illustrated in FIG. 87 includes an optical scale11 a in which the polarization direction of the polarizer is orientedone direction across the 360 degrees of a plane having the referencepoint at the center O, and an optical scale 11 b provided in a mannersurrounding the outer circumference of the optical scale 11 a androtating about the center O with the optical scale 11 a. The opticalscale 11 b is provided with signal tracks T21 and T22, each of whichoccupies 180 degrees of the plane having the reference point at thecenter O, and each of which forms a polarizer whose polarizationdirection is oriented differently. The signal tracks T21 form aconcentric polarization pattern in which the polarization direction ofthe polarizer is oriented one direction, concentrically about the centerO. The signal tracks T22 form a radial polarization pattern in which thepolarization direction of the polarizer is oriented one direction in theradial direction (moving radius direction) from the center O. An opticalsensor SE1 and an optical sensor SE2, which are the optical sensors 35arranged 180-degree symmetrical with respect to the center O, read thesignal tracks T1 a on the optical scale 11 a. Another optical sensor SE3including the optical sensor 35 reads the signal tracks T21 and T22 onthe optical scale 11 b that passes through the optical sensor SE3alternatingly.

The optical sensor SE1 includes the first optical sensor 36A and thesecond optical sensor 36B illustrated in FIG. 88, in the same manner asin the optical sensor 35 explained above. The first optical sensor 36Aincludes a first polarizing layer 39 a 1 for splitting incident light tothe light with the first polarization direction, and the firstphotoreceivers for receiving the first polarized light split by thefirst polarizing layer 39 a 1, and is capable of detecting the intensityof light with the first polarization direction. The second opticalsensor 36B includes a second polarizing layer 39 b 1 for splitting theincident light to the light with the second polarization direction, andthe second photoreceivers for receiving the second polarized light splitby the second polarizing layer 39 b 1, and is capable of detecting theintensity of light with the second polarization direction.

The optical sensor SE2 includes the first optical sensor 36A and thesecond optical sensor 36B illustrated in FIG. 89, in the same manner asin the optical sensor 35 explained above. The first optical sensor 36Aincludes a first polarizing layer 39 a 2 for splitting incident lightinto the light with a first polarization direction, and the firstphotoreceivers for receiving the first polarized light split by thefirst polarizing layer 39 a 2, and is capable of detecting the intensityof light with the first polarization direction. The second opticalsensor 36B includes a second polarizing layer 39 b 2 for splitting theincident light to the light with the second polarization direction, andthe second photoreceivers for receiving the second polarized light splitby the second polarizing layer 39 b 2, and is capable of detecting theintensity of light with the second polarization direction. Thepolarization direction detected by the first polarizing layer 39 a 1 isdifferent by 45 degrees from that detected by the first polarizing layer39 a 2. The polarization direction detected by the second polarizinglayer 39 b 1 is different by 45 degrees from that detected by the secondpolarizing layer 39 b 2.

The optical sensor SE3 also includes the first optical sensor 36A andthe second optical sensor 36B illustrated in FIG. 90, in the same manneras in the optical sensor 35 explained above. The first optical sensor36A includes a first polarizing layer 39 a 3 for splitting incidentlight into the light with the first polarization direction, and thefirst photoreceivers for receiving the first polarized light split bythe first polarizing layer 39 a 3, and is capable of detecting theintensity of light with the first polarization direction. The secondoptical sensor 36B includes a second polarizing layer 39 b 3 forsplitting the incident light to the light with the second polarizationdirection, and the second photoreceivers for receiving the secondpolarized light split by the second polarizing layer 39 b 3, and iscapable of detecting the intensity of light with the second polarizationdirection. In the optical sensors SE1, SE2, and SE3, it is morepreferable that the first photoreceivers 36 a and the secondphotoreceivers 36 b be arranged alternatingly and spaced uniformly witheach other. With such a configuration, even when a foreign substanceblocks a part of the sensing area, the chances of the firstphotoreceivers 36 a and the second photoreceivers 36 b being blocked byapproximately the same degree can be increased, so that the possibilityof the signal intensity output from one of the first photoreceivers 36 aand the second photoreceivers 36 b dropping extremely can be reduced.

Modification

FIG. 91 is a schematic for explaining an exemplary modification of theoptical scale according to the eighteenth embodiment. FIG. 92 is aschematic for explaining an exemplary modification of the optical sensoraccording to the eighteenth embodiment. The members that are the same asthose described above are assigned with the same reference numerals, andredundant explanations thereof are omitted hereunder.

An optical scale 11J illustrated in FIG. 91 includes an optical scale 11a in which the polarization direction of the polarizer is oriented onedirection across the entire 360 degrees of a plane having the referencepoint at the center O, and an optical scale 11 c provided in a mannersurrounding the outer circumference of the optical scale 11 a androtating about the center O with the optical scale 11 a. The opticalscale 11 c is provided with signal tracks T31 which form alight-shielding pattern that shields light, and signal tracks T32 whichform a translucent pattern allowing light to pass through. Each of thesignal tracks T31 and the signal tracks T32 occupies 180 degrees of theplane having the reference point at the center O. An optical sensor SE1and an optical sensor SE2, which are the optical sensors 35 arranged180-degree symmetrical with respect to the center O, read signal tracksT1 a on the optical scale 11 a. Another optical sensor SE3 in aphotodiode 36PD illustrated in FIG. 92 reads the signal tracks T31 andT32 on the optical scale 11 c passing through the optical sensor SEalternatingly. The photodiode 36PD may be any optical sensor other thana photodiode, as long as such an optical sensor is capable ofdetermining the light intensity.

Encoder

FIG. 93 is a schematic for explaining outputs from the encoder accordingto the eighteenth embodiment. FIG. 93 illustrates outputs from theencoder with the optical scale 11I illustrated in FIG. 87. The opticalscale 11 a has a polarizer whose polarization axis is uniform across theplane. The optical scale 11 a causes the polarization axis of theincident light that is incident on the optical sensors SE1 and SE2 tochange in the rotating circumferential direction, as the optical scale11 a is rotated. As described earlier, the polarization directiondetected by the first polarizing layer 39 a 1 is different from thatdetected by the first polarizing layer 39 a 2 by 45 degrees, and thepolarization direction detected by the second polarizing layer 39 b 1 isdifferent from that detected by the first polarizing layer 39 b 2 by 45degrees. Therefore, when the output from the optical sensor SE1 is asine wave illustrated in FIG. 93, the output from the optical sensor SE2will be a cosine wave. The CPU 4 c serving as a computing unit can thencalculate the differential signal V indicating a relative amount ofmovement of the optical scale 11 a with respect to each of the opticalsensors SE1 and SE2 from the intensities of the first polarized lightand the intensities of the second polarized light. However, because thedifferential signal V acquired from the optical scale 11 a repeats anincrease and decrease twice as the optical scale 11 a is rotated once,correspondingly to the rotation angle of the polarization axis, the CPU4 c serving as a computing unit needs to determine whether the rotationangle of the optical scale 11I (11J) is in a range equal to or more thanzero degrees and less than 180 degrees, or in a range equal to or morethan 180 degrees and less than 360 degrees, before calculating anabsolute angle.

Therefore, the optical scale 11 b is provided with the signal tracks T31and the signal tracks T32 each of which occupies 180 degrees of theplane having a reference point at the center O, and each of which has apolarizer with a different polarization direction. The optical sensorSE3 outputs a branch detecting signal output “branch” allowing such aborder to be identified at one position in the 360 degrees as adifferential signal, as illustrated in FIG. 93. When the optical sensorSE3 reads the optical scale 11 c, the optical sensor SE3 outputs thebranch detecting signal output “branch” allowing the border to beidentified at one position in the 360 degrees as an intensity signalrepresenting light intensity. Therefore, the CPU 4 c can determine ifthe rotation angle of the optical scale 11I (11J) is in the range equalto or more than zero degrees and less than 180 degrees or in the rangeequal to or more than 180 degrees and less than 360 degrees. Thecomputing unit 3 can identify the absolute position of the rotationangle of the rotor 10 from the differential signal of the signal tracksT11 a and the differential signal of the signal tracks T21, T21 (T31,T32). In this manner, the encoder 2 according to the eighteenthembodiment can provide an absolute encoder capable of calculating anabsolute position of the rotor 10.

Nineteenth Embodiment

FIG. 94 is a schematic for explaining an optical scale according to anineteenth embodiment of the present invention. FIGS. 95 and 96 areschematics for explaining polarizing axes of the optical sensoraccording to the nineteenth embodiment. The members that are the same asthose described above are assigned with the same reference numerals, andredundant explanations thereof are omitted hereunder.

This optical scale 11HY illustrated in FIG. 94 includes the opticalscale 11 a, and the optical scale 11 b provided in a manner surroundingthe outer circumference of the optical scale 11 a and rotating about thecenter O with the optical scale 11 a, both of which are as describedabove. The optical scale 11HY also includes the optical scale 11, whichis explained earlier, provided in a manner surrounding the outercircumference of the optical scale 11 b and rotating about the center Owith the optical scale 11 b.

The optical sensor SE1 and the optical sensor SE2 each of which includesthe optical sensors 35 and that are arranged 180-degree symmetricallywith respect to the center O read the signal tracks T1 a on the opticalscale 11 a. The optical sensor SE3 including the optical sensor 35 readsthe signal tracks T21 and the signal tracks T22 on the optical scale 11b passing across these optical sensors alternatingly.

Optical sensors SECOS and SESIN each including the optical sensor 35read the signal tracks T1 on the optical scale 11. As explained earlier,the signal tracks T1 has a wire pattern consisting of curves having awave-like form with six cycles in the 360 degrees with reference to thecenter O, and in which each of the cycles corresponds to 60 degrees.Therefore, the optical sensor SECOS is positioned at such a phase offsetfrom the optical sensor SESIN that a line extended from the opticalsensor SECOS to the center O forms an angle of 15 degrees, whichcorresponds to one quarter of the cycle, with a line extended from theoptical sensor SESIN to the center O.

The optical sensor SECOS includes the first optical sensor 36A and thesecond optical sensor 36B illustrated in FIG. 95, in the same manner asin the optical sensor 35 explained above. The first optical sensor 36Aincludes a first polarizing layer 39 a 4 for splitting incident light tothe light with the first polarization direction, and the firstphotoreceivers for receiving the first polarized light split by thefirst polarizing layer 39 a 4, and is capable of detecting the intensityof light with the first polarization direction. The second opticalsensor 36B includes a second polarizing layer 39 b 4 for splitting theincident light to the light with the second polarization direction, andthe second photoreceivers for receiving the second polarized light splitby the second polarizing layer 39 b 4, and is capable of detecting theintensity of light with the second polarization direction.

The optical sensor SESIN includes the first optical sensor 36A and thesecond optical sensor 36B illustrated in FIG. 96, in the same manner asin the optical sensor 35 explained above. The first optical sensor 36Aincludes a first polarizing layer 39 a 4 for splitting incident lightinto the light with a first polarization direction and the firstphotoreceivers for receiving the first polarized light split by thefirst polarizing layer 39 a 4, and is capable of detecting the intensityof light with the first polarization direction. The second opticalsensor 36B includes a second polarizing layer 39 b 4 for splitting theincident light to the light with the second polarization direction, andthe second photoreceivers for receiving the second polarized light splitby the second polarizing layer 39 b 4, and is capable of detecting theintensity of the light with the second polarization direction. Becausethe optical sensor SECOS and the optical sensor SESIN are positionedoffset from each other by 15 degrees, the polarization directiondetected by the optical sensor SECOS is different from that detected bythe optical sensor SESIN by 15 degrees. In the optical sensors SECOS andSESIN, it is more preferable that the first photoreceivers 36 a and thesecond photoreceivers 36 b be arranged alternatingly and spaceduniformly with each other. With such a configuration, even when aforeign substance blocks a part of the sensing area, the chances of thefirst photoreceivers 36 a and the second photoreceivers 36 b beingblocked by approximately the same degree can be increased, so that thepossibility of the signal intensity output from one of the firstphotoreceivers 36 a and the second photoreceivers 36 b droppingextremely can be reduced.

FIG. 97 is a schematic for explaining outputs from the encoder accordingto the nineteenth embodiment. The optical scale 11 a has a polarizerwhose polarization axis is uniform across the plane. The optical scale11 a causes the polarization axis of the incident light that is incidenton the optical sensors SE1 and SE2 to change in the rotatingcircumferential direction, as the optical scale 11 a is rotated. Asdescribed earlier, the polarization direction detected by the firstpolarizing layer 39 a 1 is different from that detected by the firstpolarizing layer 39 a 2 by 45 degrees. The polarization directiondetected by the second polarizing layer 39 b 1 is different from thatdetected by the first polarizing layer 39 b 2 by 45 degrees. Therefore,when the output from the optical sensor SE1 is a sine wave illustratedin FIG. 97, the output from the optical sensor SE2 will be cosine wave.The CPU 4 c serving as a computing unit can then calculate thedifferential signal V indicating a relative amount of movement of theoptical scale 11 a with respect to each of the optical sensors SE1 andSE2 from the intensities of the first polarized light and theintensities of the second polarized light. However, because thedifferential signal V acquired from the optical scale 11 a repeats anincrease and decrease twice as the optical scale 11 a is rotated once,correspondingly to the rotation angle of the polarization axis, the CPU4 c serving as a computing unit needs to determine whether the rotationangle of the optical scale 11I (11J) is in a range equal to or more thanzero degrees and less than 180 degrees, or in a range equal to or morethan 180 degrees and less than 360 degrees, before calculating anabsolute angle.

Therefore, the optical scale 11 b is provided with signal tracks T21 andT22 each of which occupies 180 degrees of the plane having a referencepoint at the center O, and each of which has a polarizer with adifferent polarization direction. The optical sensor SE3 outputs abranch detecting signal output “branch” allowing the border to beidentified at one position in the 360 degrees, as illustrated in FIG.97. Therefore, the CPU 4 c can determine if the rotation angle of theoptical scale 11HY is in the range equal to or more than zero degreesand less than 180 degrees or in the range equal to or more than 180degrees and less than 360 degrees.

FIG. 98 is a schematic for explaining outputs from the encoder accordingto the nineteenth embodiment. The optical scale 11HY has the opticalscale 11, and each of the optical sensor SECOS and the optical sensorSESIN outputs the signal intensity I(−) of the component having thefirst polarization direction and the signal intensity I(+) of thecomponent having the second polarization direction. The computing unit 3illustrated in FIG. 3 then acquires the signal intensity I(−) of thecomponent having the first polarization direction and the signalintensity I(+) of the component having the second polarization directionthat are the detection signals from the optical sensors 35. Thecomputing unit 3 then calculates the differential signal V from thesignal intensity I(−) of the component having the first polarizationdirection and the signal intensity I(+) of the component having thesecond polarization direction, following Equation (1) mentioned above.As the optical scale 11 is rotated by once, the differential signal Vindicates a waveform with six cycles. Therefore, the CPU 4 c needs todetermine to which one of 30-degree units the rotation angle of theoptical scale 11HY belongs. Therefore, the computing unit 3 identifiesone of the 30 degree-units where the absolute position of the rotationangle of the rotor 10 belongs, from the differential signal from thesignal tracks T11 a and the differential signal from the signal tracksT21, T21 illustrated in FIG. 97. The computing unit 3 then calculate amore specific rotation angle from the differential signal V illustratedin FIG. 98. In this manner, the encoder 2 can provide an absoluteencoder capable of calculating an absolute position of the rotor 10.

Modification

FIG. 99 is a schematic for explaining an exemplary modification of theencoder according to the nineteenth embodiment. FIG. 100 is a schematicfor explaining an optical sensor in the encoder illustrated in FIG. 99.FIG. 101 is a schematic for explaining the optical sensor in the encoderillustrated in FIG. 99. As illustrated in FIG. 99, the optical sensorSECOS and the optical sensor SESIN may be positioned in line with thecenter O. In this modification, the optical sensor SECOS includes thefirst optical sensor 36A and the second optical sensor 36B illustratedin FIG. 100, in the same manner as in the optical sensor 35 explainedabove. The first optical sensor 36A includes a first polarizing layer 39a 4 for splitting incident light to the light with the firstpolarization direction, and the first photoreceivers for receiving thefirst polarized light split by the first polarizing layer 39 a 4, and iscapable of detecting the intensity of light with the first polarizationdirection. The second optical sensor 36B includes a second polarizinglayer 39 b 4 for splitting the incident light to the light with thesecond polarization direction, and the second photoreceivers forreceiving the second polarized light split by the second polarizinglayer 39 b 4, and is capable of detecting the intensity of light withthe second polarization direction.

The optical sensor SESIN includes the first optical sensor 36A and thesecond optical sensor 36B illustrated in FIG. 101, in the same manner asin the optical sensor 35 explained above. The first optical sensor 36Aincludes a first polarizing layer 39 a 5 for splitting incident light tothe light with the first polarization direction, and the firstphotoreceivers for receiving the first polarized light split by thefirst polarizing layer 39 a 5, and is capable of detecting the intensityof light with the first polarization direction. The second opticalsensor 36B includes a second polarizing layer 39 b 5 for splitting theincident light to the light with the second polarization direction, andthe second photoreceivers for receiving the second polarized light splitby the second polarizing layer 39 b 5, and is capable of detecting theintensity of light with the second polarization direction.

The first polarizing layer 39 a 4 is positioned at such a phase offsetfrom the first polarizing layer 39 a 5 in such a manner that thepolarization directions detected by the respective polarizing layers areshifted by 15 degrees, which corresponds to one quarter of one cycle. Inthe same manner, the second polarizing layer 39 b 4 is positioned atsuch a phase offset from the second polarizing layer 39 b 5 that thepolarization directions detected by the respective polarizing layersbecome shifted by 15 degrees, which corresponds to one quarter of onecycle.

Alternatively, each of the optical sensors SESIN and SECOS may beprovided in plurality along the circumferential direction of the opticalscale 11HY. FIG. 102 is a schematic for explaining such an exemplarymodification of the encoder according to the nineteenth embodiment. FIG.103 is a schematic for explaining an arrangement of optical sensors inthe encoder illustrated in FIG. 102. For example, as illustrated in FIG.102, because the optical scale 11 has a wire pattern consisting ofcurves having a wave-like form with six cycles in the 360 degrees withreference to the center O, in the same manner as in the signal tracks T1described above, the optical scale 11 may have 12 pairs of opticalsensors SESIN and SECOS along the circumferential direction. In thismanner, the redundancy of the optical sensors SESIN and SECOS can beensured. As illustrated in FIG. 103, in the configuration in which eachof the optical sensors SESIN and SECOS is provided in plurality, theoptical sensor 35 may be implemented in plurality on a singlesensor-implementing substrate (e.g., a printed substrate or a siliconsubstrate) 340, at the positions corresponding to the respective opticalsensors SESIN and SECOS. Alternatively, a silicon substrate or a glasssubstrate may be used as the sensor-implementing substrate 340, and thesensors SESIN and SECOS may be implemented integrally on the onesubstrate, using the method described above (such as the methodillustrated in FIG. 17). Furthermore, the sensor-implementing substrate340 may be provided with a slit 340SL that is large enough for the shaft29 which is present on the line extended from the central axis of thecenter O to be avoided. Such a slit 340SL allows easy mounting to thecentral axis after the sensors are implemented.

Encoder

FIGS. 104 and 105 are block diagrams of the encoder according to thenineteenth embodiment. FIG. 105 is a block diagram for explaining thenoise removal circuit illustrated in FIG. 104 in detail. FIGS. 106 and107 are schematics for explaining angle detection signal outputs fromthe encoder according to the nineteenth embodiment.

As illustrated in FIG. 104, a computing unit 3A in the encoder 2includes noise removal circuits NR1, NR2 . . . , NR4, NR5 . . . , amultiplying circuit AP1, and a computing circuit CU. The computing unit3A is connected to the control unit 5 of the rotary machine such as amotor. To explain the noise removal circuit NR1 as a representativeexample, the noise removal circuit NR1 includes an alternating currentamplifier 1 NR11, a phase adjustment circuit 1 NR12, a polarityinversion circuit 1 NR13, an integration circuit 1 NR14, and a directcurrent amplifier 1 NR15, as illustrated in FIG. 105. The light source41 includes the light emitting device 41U and a driver 41 dv thatsupplies power to the light emitting device 41U. The optical sensorpackage 31 includes an optical sensor SECOS (35) having photoreceiversincluding the first optical sensor 36A and the second optical sensor36B, and a received light amplifier AMP1. The received light amplifierAMP1 is an amplifier that converts a current into a voltage, and is atransimpedance amplifier.

A reference signal ISIG generated by the signal generator SIG is inputto the driver 41 dv. The light emitting device 41U emits light based onthe reference signal ISIG, to output the light source light 71 to theoptical scale 11, 11I. The reflected light 72 (may also be thetransmissive light 73) is received by the optical sensors SECOS, SESIN,SE1, SE2, and SE3 that are photoreceivers. As illustrated in FIG. 105, areceived light signal VSIG1 amplified by the received light amplifierAMP1 is input to the noise removal circuit NR1. The noise removalcircuit NR1 is a lock-in amplifier. When the received light signal VSIG1and a reference signal IREF generated by the signal generator SIG areinput to the noise removal circuit NR1, the reference signal IREF havingphase adjusted via the phase adjustment circuit 1NR12 acts only on thereceived light signal VSIG1 that is targeted to be detected in thepolarity inversion circuit 1NR13, and the integration circuit 1NR14detects the amplitude information of the received light signal VSIG1targeted to be detected. The direct current amplifier 1NR15 amplifiesthe amplitude information of the received light signal VSIG1 thusdetected, and outputs the information to the multiplying circuit AP1illustrated in FIG. 104. The multiplying circuit AP1 generates aharmonic signal that is several times of a basic frequency from thebasic frequency. The computing circuit CU includes an absolute anglecomputing circuit AB that calculates the absolute angle described above,and an angle computation correcting circuit RE that corrects the anglecomputation from the outputs of the optical sensors SECOS, SESIN, SE1,SE2, and SE3, and a multiple rotation computing circuit ADA.

The multiple rotation computing circuit ADA computes a multiple rotationangle which includes rotations of optical scale 11HY equal to or morethan 360 degrees. When the rotor 10 is rotated, the optical scale 11 aand the optical scale 11 b are rotated by the same rotation angle as theoptical scale 11. The optical sensor SE3 outputs the branch detectingsignal output “branch” allowing the border to be identified at oneposition in the 360 degrees as a differential signal, as illustrated inFIG. 93. The computing unit 3A then becomes capable of determining theabsolute range of the rotation angle of the rotor 10 from thedifferential signals V output from SE1 and SE2, as illustrated in FIG.93, in the manner described in the eighteenth embodiment. The computingunit 3A acquires the amount of movement from the differential signals Voutput from SECOS and SESIN illustrated in FIG. 106, using the absoluterange (absolute position) thus determined as the initial position. Forexample, the computing unit 3A calculates the Lissajous patternillustrated in FIG. 107 in order to identify the absolute rotation angleof the rotor 10 having rotated with respect to the initial position,from the differential signals V output from SECOS and SESIN illustratedin FIG. 106. The Lissajous pattern illustrated in FIG. 107 is cycled sixtimes as the rotor 10 is rotated once. In this manner, the encoder 2 canprovide an absolute encoder capable of calculating an absolute positionof the rotor 10.

FIG. 108 is a schematic for explaining angle detection signal outputsfrom the encoder according to the nineteenth embodiment. FIG. 109 is aschematic for explaining angle detection signal outputs from the encoderaccording to the nineteenth embodiment. The differential signal VCOS ofSECOS and the differential signal VSIN of SESIN as illustrated in FIG.108 are differential signals V whose phases are different by λ/4. Asdescribed earlier, when a Lissajous pattern is drawn by plotting thedifferential signal VCOS to the horizontal axis and plotting thedifferential signal VSIN to the vertical axis, as illustrated in FIG.109, the Lissajous angle θLA illustrated in FIG. 109 is determined bythe rotation angle θrot illustrated in FIG. 108.

FIG. 110 is a flowchart for explaining angle detection signal outputsfrom the encoder according to the nineteenth embodiment. As illustratedin FIGS. 110 and 104, the multiple rotation computing circuit ADA in theencoder 2 reads a rotation count of the rotor 10 stored in at least oneof the RAM 4 e and the internal storage device 4 f (Step S61).

The angle computation correcting circuit RE then calculates an anglerange from the outputs of the optical sensors SE1, SE2, and SE3 (StepS62). Because the outputs from the optical scale 11 a repeats anincrease and decrease twice while the optical scale 11HY is rotatedonce, the angle computation correcting circuit RE needs to perform anangle range calculation to determine whether the rotation angle of theoptical scale 11HY is in a range equal to or more than zero degrees andless than 180 degrees, or in a range equal to or more than 180 degreesand less than 360 degrees. Within the rotational angles of the opticalscale 11HY thus identified, that is, within one of the angle range equalto or more than zero degrees and less than 180 degrees or the anglerange equal to or more than 180 degrees and less than 360 degrees, theangle computation correcting circuit RE calculates the differentialsignals V indicating the amounts of relative movement of the opticalscale 11 a with respect to the optical sensors SE1, SE2, respectively.As a result, the computing unit 3 identifies a 30-degree range (anglerange) including the absolute position of the rotation angle of therotor 10 from the differential signal corresponding to the signal tracksT11 a and the differential signal corresponding to the signal tracks T21and T22.

As described earlier, the Lissajous pattern illustrated in FIG. 107 iscycled six times while the optical scale 11 in the rotor 10 is rotatedonce. Therefore, the absolute angle computing circuit AB determineswhich one of the six cycles while which the optical scale 11 is rotatedthe rotation angle belongs, based on the 30-degree range (angle range)including the absolute position of the rotation angle of the rotor 10identified at Step S62, and calculates the specific angle (Step S63).The absolute angle computing circuit AB then establishes the Lissajousangle θLA within the cycle while which the optical scale 11 is rotatedas the rotation angle θrot. The computing circuit CU then outputs therotation angle θrot as an absolute angle (Step S64).

If the rotor 10 is still being rotated and the operation of the encoder2 is not ended (No at Step S65), the computing unit 3A returns theprocess to Step S62, and causes the angle computation correcting circuitRE to calculate the angle range from the outputs of the optical sensorsSE1, SE2, and SE3 (Step S62). If the rotation of the rotor 10 is stoppedand the operation of the encoder 2 is to be ended (Yes at Step S65), thecomputing unit 3A moves the process to Step S66.

The encoder 2 stores the rotation count for the time for which themultiple rotation computing circuit ADA is being operated as therotation count at the time of ending, in at least one of the RAM 4 e andthe internal storage device 4 f (Step S66). By adding the information ofthe rotation count that can be output by the multiple rotation computingcircuit ADA and the absolute angle that can be output by the absoluteangle computing circuit AB, the encoder 2 can output an absolute angleequal to or more than 360 degrees to the control unit 5 when the opticalscale 11HY is rotated more than once.

Twentieth Embodiment

FIG. 111 is a schematic for explaining an optical scale according to atwentieth embodiment of the present invention. FIG. 112 is a schematicfor explaining a relation between a rotation angle and an angle range inthe optical scale according to the twentieth embodiment. The membersthat are the same as those described above are assigned with the samereference numerals, and redundant explanations thereof are omittedhereunder.

This optical scale 11HW illustrated in FIG. 111 includes the opticalscale 11 a, and the optical scale 11 b provided in a manner surroundingthe outer circumference of the optical scale 11 a and rotating about thecenter O with the optical scale 11 a. The optical scale 11HW alsoincludes optical scales 11Y4, 11Y8, and 11Y16 provided in a mannersurrounding the outer circumference of the optical scale 11 b, androtating about the center O with the optical scale 11 b.

The optical scale 11HW includes wire grid patterns consisting of curveshaving a wave-like form with four cycles, eight cycles, and sixteencycles, respectively, in the 360 degrees. The intervals of the adjacentwires are the same at positions where the tangential directions of therespective wires are oriented the same. When compared are the positionsin which the tangential directions are different, the intervals are alsodifferent. An optical scale 11Y4 is provided with a wire grid patternwhose wires form a curved pattern in a wave-like form with four cyclesin the 360 degrees, in which the intervals between the adjacent wiresare constant at positions where the tangential directions are orientedthe same, and such intervals are different when compared are those atthe positions where the tangential directions are oriented differently,in the same manner as in the optical scale 11. The optical scale 11Y8 isprovided with a wire grid pattern whose wires form a curved pattern in awave-like form with eight cycles in the 360 degrees, in which theintervals between the adjacent wires are constant at positions where thetangential directions are oriented the same, and such intervals aredifferent when compared are those at the positions where the tangentialdirections are oriented differently, in the same manner as in theoptical scale 11. The optical scale 11Y16 is provided with a wire gridpattern whose wires form a curved pattern in a wave-like form withsixteen cycles in 360 degree, in which the intervals between theadjacent wires are constant at positions where the tangential directionsare oriented the same, and such intervals are different when comparedare those at the positions where the tangential directions are orienteddifferently, in the same manner as in the optical scale 11.

The optical sensor SECOS and the optical sensor SESIN are linearlyarranged toward outside in the radial direction, from the viewpoint atthe center O, as illustrated in FIG. 99, for each of the optical scales11Y4, 11Y8, and 11Y16. The optical sensor SECOS includes the firstoptical sensor 36A and the second optical sensor 36B illustrated in FIG.100, in the same manner as in the optical sensor 35 explained above. Thefirst optical sensor 36A includes a first polarizing layer 39 a 4 forsplitting incident light to the light with the first polarizationdirection, and the first photoreceivers for receiving the firstpolarized light split by the first polarizing layer 39 a 4, and iscapable of detecting the intensity of light with the first polarizationdirection. The second optical sensor 36B includes a second polarizinglayer 39 b 4 for splitting the incident light to the light with thesecond polarization direction, and the second photoreceivers forreceiving the second polarized light split by the second polarizinglayer 39 b 4, and is capable of detecting the intensity of light withthe second polarization direction.

The optical sensor SESIN includes the first optical sensor 36A and thesecond optical sensor 36B illustrated in FIG. 101, in the same manner asin the optical sensor 35 explained above. The first optical sensor 36Aincludes a first polarizing layer 39 a 5 for splitting incident light tothe light with the first polarization direction, and the firstphotoreceivers for receiving the first polarized light split by thefirst polarizing layer 39 a 5, and is capable of detecting the intensityof light with the first polarization direction. The second opticalsensor 36B includes a second polarizing layer 39 b 5 for splitting theincident light to the light with the second polarization direction, andthe second photoreceivers for receiving the second polarized light splitby the second polarizing layer 39 b 5, and is capable of detecting theintensity of light with the second polarization direction.

As illustrated in FIGS. 110 and 104, the encoder 2 causes the multiplerotation computing circuit ADA to read the rotation count of the rotor10 stored in at least one of the RAM 4 e and the internal storage device4 f (Step S61).

The angle computation correcting circuit RE then calculates the anglerange from the outputs of the optical sensors SE1, SE2, and SE3, and theoptical sensors SESIN and SECOS provided for each of the optical scale11Y4, 11Y8, 11Y16 (Step S62). Because the outputs from the optical scale11 a repeats an increase and decrease twice while the optical scale 11HWis rotated once, the angle computation correcting circuit RE needs toperform an angle range calculation to determine whether the rotationangle of the optical scale 11HW is in a range equal to or more than zerodegrees and less than 180 degrees, or in a range equal to or more than180 degrees and less than 360 degrees.

As illustrated in FIG. 112, the rotation angle θrot of the optical scale11HW belongs to one of an angle range branch Q21 that is a range equalto or more than zero degrees and less than 180 degrees, or to an anglerange branch Q22 that is a range equal to or more than 180 degrees andless than 360 degrees, on the synchronizing optical scale 11 a. Asillustrated in FIG. 112, for example, it is assumed that the rotationangle θrot of the optical scale 11HW is at a position indicated by thearrow QQ, when the absolute angle is θab. At each position MM where theabsolute angle θab exceeds 360 degrees, the multiple rotation computingcircuit ADA makes the storage described above in at least one of the RAM4 e and the internal storage device 4 f. The angle computationcorrecting circuit RE performs an angle range calculation consideringthat the position of the arrow QQ belongs to the angle range branch Q21,for example.

The angle computation correcting circuit RE calculates the angle rangefrom the outputs of the SESIN and SECOS reading the optical scale 11Y4.As illustrated in FIG. 112, the rotation angle θrot of the optical scale11HW thus identified belongs to one of an angle range branch Q41 that isa range equal to or more than 0 degrees and less than 90 degrees, anangle range branch Q42 that is a range equal to or more than 90 degreesand less than 180 degrees, an angle range branch Q43 that is a rangeequal to or more than 180 degrees and less than 270 degrees, and anangle range branch Q44 that is a range equal to or more than 270 degreesand less than 360 degrees, on the synchronizing optical scale 11Y4. Theangle computation correcting circuit RE calculates the output from theSESIN and SECOS reading the optical scale 11Y4 as the Lissajous patternillustrated in FIG. 107, assigns the angle range branches Q41, Q42, Q43,and Q44 to the respective four cycles, and performs the angle rangecalculation by considering that the position of the arrow QQcorresponding to the angle range branch Q21 belongs to the angle rangebranch Q41.

The angle computation correcting circuit RE then calculates the anglerange from the outputs of the SESIN and SECOS reading the optical scale11Y8. As illustrated in FIG. 112, the rotation angle θrot of the opticalscale 11HW thus identified belongs to one of an angle range branch Q81that is a range equal to or more than 0 degrees and less than 45degrees, an angle range branch Q82 that is a range equal to or more than45 degrees and less than 90 degrees, an angle range branch Q83 that is arange equal to or more than 90 degrees and less than 135 degrees, anangle range branch Q84 that is a range equal to or more than 135 degreesand less than 180 degrees, an angle range branch Q85 that is a rangeequal to or more than 180 degrees and less than 225 degrees, an anglerange branch Q86 that is a range equal to or more than 225 degrees andless than 270 degrees, an angle range branch Q87 that is a range equalto or more than 270 degrees and less than 315 degrees, and an anglerange branch Q88 that is a range equal to or more than 315 degrees andless than 360 degrees, on the synchronizing optical scale 11Y8. Theangle computation correcting circuit RE then calculates the output fromthe SESIN and SECOS reading the optical scale 11Y8 as the Lissajouspattern illustrated in FIG. 107, assigns the angle range branches Q81,Q82, Q83, Q84, Q85, Q86, Q87, and Q88 to the respective eight cycles,and performs the angle range calculation by considering that theposition of the arrow QQ corresponding to the angle range branch Q41belongs to the angle range branch Q82.

The angle computation correcting circuit RE then calculates the anglerange from the outputs of the SESIN and SECOS reading the optical scale11Y16. As illustrated in FIG. 112, the rotation angle θrot of theoptical scale 11HW thus identified belongs to one of an angle rangebranch Q161 that is a range equal to or more than 0 degrees and lessthan 22.5 degrees, an angle range branch Q162 that is a range equal toor more than 22.5 degrees and less than 45 degrees, an angle rangebranch Q163 that is a range equal to or more than 45 degrees and lessthan 67.5 degrees, an angle range branch Q164 that is a range equal toor more than 67.5 degrees and less than 90 degrees, an angle rangebranch Q165 that is a range equal to or more than 90 degrees and lessthan 112.5 degrees, an angle range branch Q166 that is a range equal toor more than 112.5 degrees and less than 135 degrees, an angle rangebranch Q167 that is a range equal to or more than 135 degrees and lessthan 157.5 degrees, an angle range branch Q168 that is a range equal toor more than 157.5 degrees and less than 180 degrees, an angle rangebranch Q169 that is a range equal to or more than 180 degrees and lessthan 202.5 degrees, an angle range branch Q1610 that is a range equal toor more than 202.5 degrees and less than 225 degrees, an angle rangebranch Q1611 that is a range equal to or more than 225 degrees and lessthan 247.5 degrees, an angle range branch Q1612 that is a range equal toor more than 247.5 degrees and less than 270 degrees, an angle rangebranch Q1613 that is a range equal to or more than 270 degrees and lessthan 292.5 degrees, an angle range branch Q1614 that is a range equal toor more than 292.5 degrees and less than 315 degrees, an angle rangebranch Q1615 that is a range equal to or more than 315 degrees and lessthan 337.5 degrees, and an angle range branch Q1616 that is a rangeequal to or more than 337.5 degrees and less than 360 degrees, on thesynchronizing optical scale 11Y16. The angle computation correctingcircuit RE calculates the output from the SESIN and SECOS reading theoptical scale 11Y16 as the Lissajous pattern illustrated in FIG. 107,and assigns the angle range branches Q161, Q162, Q163, Q164, Q165, Q166,Q167, Q168, Q169, Q1610, Q1611, Q1612, Q1613, Q1614, Q1615, and Q1616 tothe respective sixteen cycles, and performs the angle range calculationby considering that the position of the arrow QQ corresponding to theangle range branch Q82 belongs to the angle range branch Q163.

As described earlier, the absolute angle computing circuit ABestablishes the Lissajous angle θLA in the third cycle, while which theoptical scale 11Y16 is rotated, as the rotation angle θrot, based on theangle range branch Q163 identified at Step S62. The computing circuit CUthen outputs the rotation angle θrot as the absolute angle (Step S64).

If the rotor 10 is still being rotated and the operation of the encoder2 is not ended (No at Step S65), the computing unit 3A returns theprocess to Step S62, and causes the angle computation correcting circuitRE to calculate the angle range from the outputs of the optical sensorsSE1, SE2, and SE3 (Step S62). If the rotation of the rotor 10 is stoppedand the operation of the encoder 2 is to be ended (Yes at Step S65), thecomputing unit 3A moves the process to Step S66.

The encoder 2 stores the rotation count, that is the number of times theposition MM is passed, while the multiple rotation computing circuit ADAis being operated, as the rotation count at the time of ending, in atleast one of the RAM 4 e and the internal storage device 4 f (Step S66).By adding the information of the rotation count that can be output bythe multiple rotation computing circuit ADA and the absolute angle thatcan be output by the absolute angle computing circuit AB, the encoder 2can output an absolute angle equal to or more than 360 degrees to thecontrol unit 5 when the optical scale 11HY is rotated more than once.

Twenty-First Embodiment

FIGS. 113-1 and 113-2 are schematics for explaining an optical scaleaccording to a twenty-first embodiment of the present invention. FIGS.114-1 to 118-4 are schematics for explaining a relation between arotation angle and a Lissajous angle in the optical scale according tothe twenty-first embodiment. FIGS. 119-1 to FIG. 119-4 are schematicsfor explaining a relation between a rotation angle and a Lissajous anglein an optical scale according to a comparative example. The members thatare the same as those described above are assigned with the samereference numerals, and redundant explanations thereof are omittedhereunder.

As illustrated in FIG. 113-1, an optical scale 11HX includes an opticalscale 11Y11 provided in a manner surrounding the outer circumference ofan optical scale 11Y5 and rotating about the center O with the opticalscale 11Y5.

The optical scale 11 is provided with a wire grid pattern whose wiresform a curved pattern in a wave-like form with six cycles in the 360degrees, in which the intervals between the adjacent wires are constantat positions where the tangential directions are oriented the same, andsuch intervals are different when compared are those at the positionswhere the tangential directions are oriented differently. The opticalscale 11Y5 is provided with a wire grid pattern whose wires form acurved pattern in a wave-like form with five and eleven cycles in the360 degrees, in which the intervals between the adjacent wires areconstant at positions where the tangential directions are oriented thesame, and such intervals are different when compared are those at thepositions where the tangential directions are oriented differently, inthe same manner as in the optical scale 11. The optical sensor SESIN ispositioned at such a phase offset from the optical sensor SECOS that aline extended from the optical sensor SECOS to the center O forms anangle θY5, which corresponds to one quarter of the cycle, with a lineextended from the optical sensors SESIN to the center O, when λ denotesone cycle of the wire pattern.

The optical scale 11Y11 is provided with a wire grid pattern whose wiresform a curved pattern in a wave-like form with eleven cycles in the 360degrees, in which the intervals between the adjacent wires are constantat positions where the tangential directions are oriented the same, andsuch intervals are different when compared are those at the positionswhere the tangential directions are oriented differently, in the samemanner as in the optical scale 11. The optical sensor SESIN ispositioned at such a phase offset from the optical sensor SECOS that anangle formed by a line extended from the optical sensor SECOS to thecenter O forms an angle θY11, which corresponds to λ/4 cycle, with aline extended from the optical sensor SESIN to the center O, when λdenotes one cycle of the wire pattern.

The number of wave-like forms (number of cycles) in the wire pattern onthe inner optical scale 11Y5 which is “5” and the number of wave-likeforms (number of cycles) in the wire pattern on the outer optical scale11Y11 which is “11” are in a mutually-prime relation, and a relation inwhich the larger number of wave-like forms (number of cycles) is not adivisor of the smaller number of wave-like forms (number of cycles). Inthis manner, the number of wave-like forms (number of cycles) in thewire pattern on the inner optical scale 11Y5, which is “5”, and thenumber of wave-like forms (number of cycles) in the wire pattern on theouter optical scale 11Y11, which is “11”, are integers not having acommon divisor except for one. The number of wave-like forms (number ofcycles) in the wire pattern on the inner optical scale 11Y5 “5” and thenumber of wave-like forms (number of cycles) in the wire pattern on theouter optical scale 11Y11 “11” are mutually prime.

An optical scale 11HZ illustrated in FIG. 113-2 includes optical scales11Y11 a, 11Y11 b provided in a manner surrounding the outercircumference of optical scales 11Y5 a, 11Y5 b and rotating about thecenter O with the optical scales 11Y5 a, 11Y5 b. The optical scales 11Y5a, 11Y5 b have the same wire pattern as that on the optical scale 11Y5.In the optical scales 11Y5 a and 11Y5 b, the optical scale 11Y5 b isprovided in a manner surrounding the outer circumference of the opticalscale 11Y5 a, and the wire pattern of the optical scale 11Y5 b ispositioned at such a phase offset from that on the optical scale 11Y5 aby θY5 which corresponds to one quarter of the cycle, when λ denotes onecycle of the wire pattern.

The optical scales 11Y11 a and 11Y11 b have the same wire pattern asthat on the optical scale 11Y11. In the optical scales 11Y11 a, 11Y11 b,the optical scale 11Y11 b is provided in a manner surrounding the outercircumference of the optical scale 11Y11 a, and the wire pattern of theoptical scale 11Y11 b is positioned at such a phase offset from that onthe optical scale 11Y11 a by θY11 which corresponds to one quarter ofthe cycle, when λ denotes one cycle of the wire pattern.

With such a structure, on the optical scale 11HZ illustrated in FIG.113-2, the optical sensor SECOS and the optical sensor SESIN areprovided for each of the optical scales 11Y5 a, 11Y5 b, 11Y11 a, and11Y11 b, and linearly positioned alternatingly toward outside of theradial direction from the viewpoint of the center O. The optical scale11HX illustrated in FIG. 113-1 can reduce the number of optical scalessurrounding the outer circumference that is outside of the radialdirection, compared with the optical scale 11HZ illustrated in FIG.113-2, so that the size of the rotor 10 can be reduced.

An operation of the encoder 2 according to the twenty-first embodimentwill now be explained. FIGS. 114-1 to 118-4 are schematics forexplaining a relation between a rotation angle and a Lissajous angle inthe optical scales 11Y5 and 11Y11 according to the twenty-firstembodiment. As illustrated in FIGS. 110 and 104, in the encoder 2, themultiple rotation computing circuit ADA reads the rotation count of therotor 10 stored in at least one of the RAM 4 e and the internal storagedevice 4 f (Step S61).

The angle computation correcting circuit RE then calculates the anglerange from the outputs of the SESIN and SECOS that are provided for eachof the optical scales 11Y5 and 11Y11 (Step S62). To begin with, for asingle rotation of the optical scale 11HX, the Lissajous pattern for theinner optical scale 11Y5 illustrated in FIG. 114-1 is cycled five timesas the rotor 10 is rotated once. For a single rotation of the opticalscale 11HX, the Lissajous pattern for the outer optical scale 11Y11illustrated in FIG. 114-2 is cycled 11 times as the rotor 10 is rotatedonce. Therefore, when the Lissajous pattern of the inner optical scale11Y5 illustrated in FIG. 114-1 is folded at an angle acquired bydividing 360-degree angle corresponding to one rotation of the rotor 10by 11 that is the largest number of cycles on the outer optical scale11Y11, a branch plot with 11 branches each representing an angle rangeof the optical scale 11Y5, as illustrated in FIG. 114-3, is achieved.The angle computation correcting circuit RE then calculates theLissajous angle of the inner optical scale 11Y5, and acquires the anglerange to which the rotation angle of the outer optical scale 11Y11belongs from the Lissajous angle of the inner optical scale 11Y5.

Similarly, when the Lissajous pattern of the outer optical scale 11Y5illustrated in FIG. 114-2 is folded at an angle acquired by dividing360-degree angle corresponding to one rotation of the rotor 10 by 11that is the largest number of cycles on the outer optical scale 11Y11, aplot with 11 overlapping branches each representing an angle range onthe optical scale 11Y11 is achieved, as illustrated in FIG. 114-4. Theangle computation correcting circuit RE calculates the relation betweenthe rotation angle of the optical scale 11Y11 and the Lissajous angleillustrated in FIG. 114-4 from the angle range at which the rotationangle of the optical scale 11Y11 is positioned, and calculates thespecific angle (Step S63).

As described earlier, the absolute angle computing circuit ABestablishes the Lissajous angle θLA in the third cycle at which theoptical scale 11Y16 is rotating as the rotation angle θrot, based on theangle range branch Q163 identified at Step S63. The computing circuit CUthen outputs the rotation angle θrot as the absolute angle (Step S64).

If the rotor 10 is still being rotated and the operation of the encoder2 is not ended (No at Step S65), the computing unit 3A returns theprocess to Step S62, and causes the angle computation correcting circuitRE to calculate the angle range from the outputs of the optical sensorsSE1, SE2, and SE3 (Step S62). If the rotation of the rotor 10 is stoppedand the operation of the encoder 2 is to be ended (Yes at Step S65), thecomputing unit 3A moves the process to Step S66.

The encoder 2 stores the rotation count for the time for which themultiple rotation computing circuit ADA is being operated as therotation count at the time of ending, in at least one of the RAM 4 e andthe internal storage device 4 f (Step S66). By adding the information ofthe rotation count that can be output by the multiple rotation computingcircuit ADA and the absolute angle that can be output by the absoluteangle computing circuit AB, the encoder 2 can output an absolute angleequal to or more than 360 degrees to the control unit 5 when the opticalscale 11HX is rotated more than once.

Modification

FIGS. 115-1 to 115-4 are schematics for explaining a relation betweenthe rotation angle and the Lissajous angle when the inner optical scalehas a wire grid pattern such as that on the optical scale 11 a (a wiregrid pattern corresponding to a curve in a wave-like form with twocycles in the 360 degrees), and the outer optical scale has a wire gridpattern curved in a wave-like form with five cycles in the 360 degrees.When the Lissajous pattern of the inner optical scale illustrated inFIG. 115-1 is folded at an angle acquired by dividing 360-degree anglecorresponding to one rotation of the rotor 10 by five which is themaximum number of cycles on the outer optical scale, as illustrated inFIG. 115-2, a branch plot with five branches each representing an anglerange of the inner optical scale is achieved, as illustrated in FIG.115-3. Similarly, when the Lissajous pattern of the outer optical scaleillustrated in FIG. 115-2 is folded at an angle acquired by dividing360-degree angle corresponding to one rotation of the rotor 10 by fivewhich is the maximum number of cycles on the outer optical scale, a plotwith five overlapping branches each representing an angle range of theouter optical scale is achieved, as illustrated in FIG. 115-4. Thenumber of wave-like forms (number of cycles) in the wire pattern on theinner optical scale and the number of wave-like forms (number of cycles)in the wire pattern on the outer optical scale are in a mutually-primerelation, and a relation in which the larger number of wave-like forms(number of cycles) is not a divisor of the smaller number of wave-likeforms (number of cycles). Therefore, “two” which is the number ofwave-like forms (number of cycles) in the wire pattern on the inneroptical scale and “five” which is the number of wave-like forms (numberof cycles) in the wire pattern on the outer optical scale are integersnot having a common divisor except for one. Furthermore, “two” which isthe number of wave-like forms (number of cycles) in the wire pattern onthe inner optical scale and “five” which is the number of wave-likeforms (number of cycles) in the wire pattern on the outer optical scaleare mutually prime.

FIGS. 116-1 to 116-4 are schematics for explaining a relation betweenthe rotation angle and the Lissajous angle when the inner optical scalehas a wire grid pattern such as that on the optical scale 11 a (a wiregrid pattern corresponding to a curve in a wave-like form with twocycles in the 360 degrees), and the wire pattern on the outer opticalscale has a wire grid pattern curved in a wave-like form with threecycles in the 360 degrees. When the Lissajous pattern of the inneroptical scale illustrated in FIG. 116-1 is folded at an angle acquiredby dividing 360-degree angle corresponding to one rotation of the rotor10 by three which is the maximum number of cycles on the outer opticalscale illustrated in FIG. 116-2, a branch plot with three branches eachrepresenting an angle range of the inner optical scale is achieved, asillustrated in FIG. 116-3. Similarly, when the Lissajous pattern of theouter optical scale illustrated in FIG. 116-2 is folded at an angleacquired by dividing 360-degree angle corresponding to one rotation ofthe rotor 10 by three which is the maximum number of cycles on the outeroptical scale, a plot with three overlapping branches each representingan angle range of the outer optical scale is achieved, as illustrated inFIG. 116-4. The number of wave-like forms (number of cycles) in the wirepattern on the inner optical scale and the number of wave-like forms(number of cycles) in the wire pattern on the outer optical scale are ina mutually-prime relation, and a relation in which the larger number ofwave-like forms (number of cycles) is not a divisor of the smallernumber of wave-like forms (number of cycles). Therefore, “two” which isthe number of wave-like forms (number of cycles) in the wire pattern onthe inner optical scale and “three” which is the number of wave-likeforms (number of cycles) in the wire pattern on the outer optical scaleare integers not having a common divisor except for one. Furthermore,“two” which is the number of wave-like forms (number of cycles) in thewire pattern on the inner optical scale and “three” which is the numberof wave-like forms (number of cycles) in the wire pattern on the outeroptical scale are mutually prime.

FIGS. 117-1 to 117-4 are schematics for explaining a relation betweenthe rotation angle and the Lissajous angle when the inner optical scalehas a wire grid pattern whose wires form a curved pattern in a wave-likeform with three cycles in the 360 degrees, the outer optical scale has awire grid pattern whose wires form a curved pattern in a wave-like formwith 11 cycles in the 360 degrees. When the Lissajous pattern of theinner optical scale illustrated in FIG. 117-1 is folded at an angleacquired by dividing 360-degree angle corresponding to one rotation ofthe rotor 10 by 11 which is the maximum number of cycles on the outeroptical scale, as illustrated in FIG. 117-2, a branch plot with 11branches each representing an angle range of the inner optical scale isachieved, as illustrated in FIG. 117-3. Similarly, when the Lissajouspattern of the outer optical scale illustrated in FIG. 117-2 is foldedat an angle acquired by dividing 360-degree angle corresponding to onerotation of the rotor 10 by 11 which is the maximum number of cycles onthe outer optical scale, a plot with 11 overlapping branches eachrepresenting an angle range of the outer optical scale is achieved, asillustrated in FIG. 117-4. The number of wave-like forms (number ofcycles) in the wire pattern on the inner optical scale and the number ofwave-like forms (number of cycles) in the wire pattern on the outeroptical scale are in a mutually-prime relation, and a relation in whichthe larger number of wave-like forms (number of cycles) is not a divisorof the smaller number of wave-like forms (number of cycles). In thismanner, “three” which is the number of wave-like forms (number ofcycles) in the wire pattern on the inner optical scale and “11” which isthe number of wave-like forms (number of cycles) in the wire pattern onthe outer optical scale are integers not having a common divisor exceptfor one. Furthermore, “three” which is the number of wave-like forms(number of cycles) in the wire pattern on the inner optical scale and“11” which is the number of wave-like forms (number of cycles) in thewire pattern on the outer optical scale are mutually prime.

FIGS. 118-1 to 118-4 are schematics for explaining a relation betweenthe rotation angle and the Lissajous angle when the inner optical scalehas a wire grid pattern whose wires form a curved pattern in a wave-likeform with five cycles in the 360 degrees, and the outer optical scalehas a wire grid pattern whose wire form a curved pattern in a wave-likeform with 12 cycles in the 360 degrees. When the Lissajous pattern ofthe inner optical scale illustrated in FIG. 118-1 is folded at an angleacquired by dividing 360-degree angle corresponding to one rotation ofthe rotor 10 by 12 which is the maximum number of cycles on the outeroptical scale as illustrated in FIG. 118-2, a branch plot with 12branches each representing an angle range of the inner optical scale isachieved, as illustrated in FIG. 118-3. Similarly, when the Lissajouspattern of the outer optical scale illustrated in FIG. 118-2 is foldedat an angle acquired by dividing 360-degree angle corresponding to onerotation of the rotor 10 by 12 which is the maximum number of cycles onthe outer optical scale, a plot with 12 overlapping branches eachrepresenting an angle range of the outer optical scale is achieved, asillustrated in FIG. 118-4. The number of wave-like forms (number ofcycles) in the wire pattern on the inner optical scale and the number ofwave-like forms (number of cycles) in the wire pattern on the outeroptical scale are integers not having a common divisor except for one,and the larger number of wave-like forms (number of cycles) and thesmaller number of wave-like forms (number of cycles) are mutually prime.In the examples explained above, a pattern with a larger number ofwave-like forms (number of cycles) is provided outside, but such apattern may also be provided inside, without limitation to the outside.However, it is more preferable to place the pattern with a larger numberof wave-like forms to the outside, from the viewpoint of sensitivity.

COMPARATIVE EXAMPLE

FIGS. 119-1 to 119-4 are schematics for explaining a relation betweenthe rotation angle and the Lissajous angle when the inner optical scalehas a wire grid pattern whose wires form a curved pattern in a wave-likeform with three cycles in the 360 degrees, and the outer optical scalehas a wire grid pattern whose wire form a curved pattern in a wave-likeform with 12 cycles in the 360 degrees. The number of wave-like forms(number of cycles) in the wire pattern on the inner optical scale andthe number of wave-like forms (number of cycles) in the wire pattern onthe outer optical scale are integers that have three as a divisor otherthan one. In other words, these are in a relation in which the largernumber of wave-like forms (number of cycles) is a divisor of the smallernumber of wave-like forms (number of cycles). In this comparativeexample, when the Lissajous pattern of the inner optical scaleillustrated in FIG. 119-1 is folded at an angle acquired by dividing360-degree angle corresponding to one rotation of the rotor 10 by 12which is the maximum number of cycles on the outer optical scale asillustrated in FIG. 119-2, the Lissajous angle for the inner opticalscale and the Lissajous angle for the outer optical scale overlap eachother, in the manner illustrated in FIG. 119-3. Therefore, even if anangle range of the outer optical scale illustrated in FIG. 119-4 iscalculated by folding the Lissajous pattern of the outer optical scaleillustrated in FIG. 119-2 at an angle acquired by dividing 360-degreeangle corresponding to one rotation of the rotor 10 by 12 which is themaximum number of cycles on the outer optical scale, the encoder 2 isnot capable of calculating an absolute angle unambiguously.

Twenty-Second Embodiment

FIG. 120 is a flowchart for explaining an operation of a torquedetection apparatus according to a twenty-second embodiment of thepresent invention. Explained in the twenty-second embodiment is anoperation in which the torque detection apparatus 200 in the electricpower steering apparatus 80 according to the ninth embodiment is used todetect steering torque. The members that are the same as those describedabove are assigned with the same reference numerals, and redundantexplanations thereof are omitted hereunder.

A torque sensor explained in the embodiments described above can be usedas the torque sensor 91 a in the electric power steering apparatus 80.The torque sensor 91 a detects a steering force of a driver communicatedvia the steering wheel 81 to the input shaft 82 a as steering torque.The speed sensor 91 v detects the running speed of a vehicle on whichthe electric power steering apparatus 80 is mounted. The ECU 90 iselectrically connected to the brushless motor 101, the torque sensor 91a, and the speed sensor 91 v. The torque sensor 91 a can output arotation angle of the steering operation to the ECU 90. Such a torquesensor 91 a is also referred to as a torque angle sensor.

As illustrated in FIG. 120, the torque detection apparatus 200illustrated in FIG. 35 serving as the torque sensor 91 a reads therotation count of the first rotating shaft 110A or the second rotatingshaft 110B stored in at least one of the RAM 4 e and the internalstorage device 4 f (Step S71).

The torsional angle of the first rotating shaft 110A or the secondrotating shaft 110B is in a range approximately from ±5 degrees to ±10degrees, and the first rotating shaft 110A and the second rotating shaft110B are rotated with a steering operation of a steerer or the likeinside of the housing 120. Therefore, in the torque detection apparatus200, the configuration of the encoder 2 described above is applied so asto output the rotation angle of the first rotating shaft 110A or thesecond rotating shaft 110B. In the torque detection apparatus 200, it isalso possible to apply the configuration of the encoder 2 describedabove to output the rotation angles of the first rotating shaft 110A andthe second rotating shaft 110B. Alternatively, the torque detectionapparatus 200 may apply the configuration of the encoder 2 describedabove to calculate and to output an average of the rotation angles ofthe first rotating shaft 110A and the second rotating shaft 110B. As theoptical scales 11AT and 11BT, the optical scales 11HT, 11HW, 11HX, 11HY,11HZ, 11Y4, 11Y5, 11Y8, 11Y11, and 11Y12 described above may be used,for example. In this manner, the torque detection apparatus 200 canoutput the rotation angle as an absolute angle.

For example, the torque detection apparatus 200 calculates an anglerange following the same process at Step 62 in the nineteenth, thetwentieth, the twenty-first, and the twenty-second embodiments describedabove (Step S72).

The torque detection apparatus 200 then calculates a specific anglefollowing the same process at Step 63 in the nineteenth, the twentieth,the twenty-first, and the twenty-second embodiments described above(Step S73).

The torque detection apparatus 200 then outputs an absolute anglefollowing the same process at Step 64 in the nineteenth, the twentieth,the twenty-first, and the twenty-second embodiments described above(Step S74).

The torque detection apparatus 200 then causes the optical sensor 35ATand the optical sensor 35BT to detect the transmissive light 73AT and73BT, respectively, that are the light source light 71AT and 71BT havingpassed through the optical scales 11AT and 11BT and being incident onthese optical sensors. The computing unit 3 calculates a relativeposition of the first rotating shaft 110A with respect to the opticalsensor package 31AT in the torque sensor 101A from the detection signalfrom the optical sensor 35AT. The computing unit 3 also calculates arelative position of the second rotating shaft 110B with respect to theoptical sensor package 31BT in the torque sensor 101A from the detectionsignal from the optical sensor 35BT.

The computing unit 3 stores the torsional elastic coefficient of thetorsion bar 129 in the RAM 4 e and the internal storage device 4 f.Torque is proportional to the torsional elastic coefficient of thetorsion bar 129. Therefore, in order to acquire torsion, the computingunit 3 calculates the rotational displacement (the amount ofdisplacement) of the rotation angle of the first rotating shaft 110A andthe rotation angle of the second rotating shaft 110B. The computing unit3 can then calculate the torque from the elastic coefficient of thetorsion bar 129 and the information of the relative position of thefirst rotating shaft 110A and the second rotating shaft 110B. Thecomputing unit 3 then outputs the torque to the control unit 5 of arotary machine (motor) or the like, as a control signal (Step S75).

The ECU 90 controls the operation of the brushless motor 101. The ECU 90acquires a signal from each of the torque sensor 91 a and the speedsensor 91 v. In other words, the ECU 90 acquires the steering torque Tfrom the torque sensor 91 a, and acquires the running speed Vb of thevehicle from the speed sensor 91 v. To the ECU 90, a power is suppliedfrom a power supply unit (e.g., buttery on the vehicle) 99 while theignition switch 98 is turned ON. The ECU 90 calculates an assistingsteering command value for an assisting command, based on the steeringtorque T and the running speed Vb. The ECU 90 adjusts a power X to besupplied to the brushless motor 101 based on the assisting steeringcommand value thus calculated. The ECU 90 acquires information of aninductive voltage from the brushless motor 101 as operation informationY.

The steering force of the steerer (driver) input to the steering wheel81 is communicated via the input shaft 82 a to the decelerator 92 in thesteering force assisting mechanism 83. At this time, the ECU 90 acquiresthe steering torque T input to the input shaft 82 a from the torquesensor 91 a, and acquires the running speed Vb from the speed sensor 91v. The ECU 90 then controls the operation of the brushless motor 101.The assisting steering torque generated by the brushless motor 101 iscommunicated to the decelerator 92.

The steering torque (including the assisting steering torque) output viathe output shaft 82 b is communicated to the lower shaft 85 via theuniversal joint 84, and further communicated to the pinion shaft 87 viathe universal joint 86. The steering force communicated to the pinionshaft 87 is communicated to the tie rod 89 via the steering gear 88,whereby causing a steered wheel to rotate.

If the operation of the electric power steering apparatus 80 is stillcontinuing and the operation of the torque detection apparatus 200 isnot ended (No at Step S76), the computing unit 3 returns the process toStep S72, and calculates the angle range (Step S72). If the operation ofthe electric power steering apparatus 80 is to be ended (Yes at StepS76), the computing unit 3 moves the process to Step S77.

The torque detection apparatus 200 stores the rotation count of the timefor which the first rotating shaft 110A or the second rotating shaft110B is being operated as the rotation count at the time of ending, inat least one of the RAM 4 e and the internal storage device 4 f (StepS77).

As described earlier, in the electric power steering apparatus 80, thefirst rotating shaft and the second rotating shaft of the torque sensoraccording to the embodiment are mounted on the steering shaft so thatthe torque detection apparatus 200 can detect steering torque, arotation count, and a steered angle of the steering.

With this structure, the optical sensor can detect a change in thepolarization direction of the transmissive light or the reflected lightin a manner less affected by foreign substances. In this manner, thereliability of the electric power steering apparatus can be improved.

REFERENCE SIGNS LIST

-   -   1, 1A, 1B, 1C, 1D, 1E encoder unit    -   2 encoder    -   3 computing unit    -   5 control unit    -   10, 10A rotor    -   11, 11 a, 11A, 11B, 11I, 11J, 11AT, 11BT, 11CT, 11DT, 11ET,        11FT, 11GT, 11HT, 11HW, 11HX, 11HY, 11HZ, 11Y4, 11Y5, 11Y8,        11Y11, 11Y12 optical scale    -   20, 20A stator    -   20B, 20C mount member    -   21 bearing    -   29 shaft    -   31, 31A, 31B, 31AT, 31BT optical sensor package    -   35, 36A, 36B, 35AT, 35BT optical sensor    -   36Ka, 36Kb sensor base    -   36 a first photoreceiver    -   36 b second photoreceiver    -   41, 41AT, 41BT light source    -   71, 71AT, 71BT light source light    -   72, 72AT, 72BT reflected light    -   73, 73AT, 73BT transmissive light    -   101A, 101B, 101C, 101D, 101E, 101F, 101G, 101H torque sensor    -   110A, 110B, 110C, 110D rotating shaft    -   120 housing    -   120B, 120C mount member    -   126A, 126B bearing    -   200 torque detection apparatus    -   C1, C2, Ls1, Ls2 sensing area    -   g, g1, g2, g3, g4 wires

The invention claimed is:
 1. A torque detection apparatus that detectstorque using torsion of a torsion bar, the torque detection apparatuscomprising: a first rotating shaft and a second rotating shaft that areconnected with a torsion bar in which torsion is produced when torque isapplied; a plurality of optical scales that move with rotations of thefirst rotating shaft and the second rotating shaft, respectively; anoptical sensor that is paired with the optical scale, and detectspolarization of transmissive light or reflected light, the polarizationvarying depending on a position where light source light is passedthrough or reflected on the optical scale; and a computing unit thatcomputes a relative rotational angle of the optical scale with respectto the optical sensor, and computes rotational displacements of thefirst rotating shaft and the second rotating shaft, wherein a pluralityof wires, having a non-circular configuration, are arranged on theoptical scale so that the plurality of wires do not intersect with eachother and each of tangential directions of the wires changescontinuously.
 2. An electric power steering apparatus comprising: thetorque detection apparatus according to claim 1, wherein the firstrotating shaft and the second rotating shaft are mounted on a steeringshaft.
 3. The torque detection apparatus according to claim 1, whereinthe tangential directions of the wires on the optical scale are orientedsame among areas in which intervals between adjacent wires are same, andthe tangential directions of the wires are oriented differently amongareas in which the intervals are different.
 4. The torque detectionapparatus according to claim 3, wherein the optical sensor uses a partof the wires whose tangential directions are oriented same as a sensingarea, and receives incident light that is the light source light passedthrough or reflected on the sensing area and being incident on theoptical sensor.
 5. The torque detection apparatus according to claim 1,wherein each of the tangential directions changes cyclically.
 6. Thetorque detection apparatus according to claim 5, wherein the opticalscale includes: a first grid pattern having a first cycle at which eachof the tangential directions changes cyclically; and a second gridpattern having a second cycle at which each of the tangential directionschanges cyclically and in which the number of cycles per one rotation isdifferent from that of the first cycle.
 7. The torque detectionapparatus according to claim 6, wherein the number of first cycles perone rotation and the number of second cycles per one rotation aremutually prime.
 8. The torque detection apparatus according to claim 1,further comprising a protection layer or a substrate covering the wires.9. The torque detection apparatus according to claim 1, wherein thewires are provided as a plurality of layers in a thickness direction inwhich the transmissive light or the reflected light is incident.
 10. Thetorque detection apparatus according to claim 1, wherein the opticalsensor comprises: a first polarizing layer that splits incident lightthat is the transmissive light or the reflected light to a firstpolarization direction; a second polarizing layer that splits theincident light to a second polarization direction; a first photoreceiverthat receives first polarized light split by the first polarizing layer;and a second photoreceiver that receives second polarized light split bythe second polarizing layer.
 11. The torque detection apparatusaccording to claim 10, wherein the first photoreceiver and the secondphotoreceiver on the optical sensor are positioned alternatingly andspaced uniformly with each other.
 12. The torque detection apparatusaccording to claim 10, wherein a polarization axis of the firstpolarized light is relatively different from a polarization axis of thesecond polarized light by 90 degrees.
 13. The torque detection apparatusaccording to claim 10, wherein the first photoreceiver and the secondphotoreceiver have a comb-like shape engaging and spaced uniformly witheach other.
 14. The torque detection apparatus according to claim 10,further comprising a light-shielding film that stops the incident lightthat is incident on the first photoreceiver and the secondphotoreceiver.
 15. The torque detection apparatus according to claim 1,wherein the computing unit calculates an absolute rotation angle of atleast one of the first rotating shaft and the second rotating shaft froma relative rotation angle of the optical scale with respect to theoptical sensor, and outputs a detected torque that is acquired from therotational displacements of the first rotating shaft and the secondrotating shaft, and the absolute rotation angle.